Implemented the User Agent middleware (#6)

This PR contains the work done to implement the `UserAgentMiddleware` middleware that includes user agent information into a header of the requests sent by the `Client` type, as defined in the [Discogs documentation](https://www.discogs.com/developers/#page:home,header:home-general-information). For this purpose, the `CamelCaseValidationRule`, `SemanticVersionValidationRule` and `URLValidationRule` types were implemented and integrated into the existing `ValidateInputUseCase` type.

Reviewed-on: #6
Co-authored-by: Javier Cicchelli <javier@rock-n-code.com>
Co-committed-by: Javier Cicchelli <javier@rock-n-code.com>

Tests/DiscogsService/Cases/Internal/Use Cases/ValidateInputUseCaseTests.swift

@@ -22,6 +22,20 @@ struct ValidateInputUseCaseTests {
     // MARK: Functions
     
 #if swift(>=6.2)
+    @Test(arguments: zip(
+        Input.inputsAgentName,
+        Output.inputsAgentName
+    )) func `validate camel case`(
+        input: String,
+        expects error: InputValidationError?
+    ) async throws {
+        try assertValidate(
+            rule: .agentName,
+            input: input,
+            expects: error
+        )
+    }
+
     @Test(arguments: zip(
         Input.inputsNotEmpty,
         Output.inputsNotEmpty
@@ -91,7 +105,49 @@ struct ValidateInputUseCaseTests {
             expects: error
         )
     }
+    
+    @Test(arguments: zip(
+        Input.inputsSemanticVersion,
+        Output.inputsSemanticVersion
+    )) func `validate semantic version`(
+        input: String?,
+        expects error: InputValidationError?
+    ) async throws {
+        try assertValidate(
+            rule: .semanticVersion,
+            input: input,
+            expects: error
+        )
+    }
+    
+    @Test(arguments: zip(
+        Input.inputsURL,
+        Output.inputsURL
+    )) func `validate url`(
+        input: String?,
+        expects error: InputValidationError?
+    ) async throws {
+        try assertValidate(
+            rule: .url,
+            input: input,
+            expects: error
+        )
+    }
 #else
+    @Test("validate camel case", arguments: zip(
+        Input.inputsCamelCase,
+        Output.inputsCamelCase
+    )) func validateCamelCase(
+        input: String,
+        expects error: InputValidationError?
+    ) async throws {
+        try assertValidate(
+            rule: .camelCase,
+            input: input,
+            expects: error
+        )
+    }
+
     @Test("validate not empty", arguments: zip(
         Input.inputsNotEmpty,
         Output.inputsNotEmpty
@@ -161,6 +217,34 @@ struct ValidateInputUseCaseTests {
             expects: error
         )
     }
+    
+    @Test("validate semantic version", arguments: zip(
+        Input.inputsSemanticVersion,
+        Output.inputsSemanticVersion
+    )) func validateSemanticVersion(
+        input: String?,
+        expects error: InputValidationError?
+    ) async throws {
+        try assertValidate(
+            rule: .semanticVersion,
+            input: input,
+            expects: error
+        )
+    }
+    
+    @Test("validate url", arguments: zip(
+        Input.inputsURL,
+        Output.inputsURL
+    )) func validateURL(
+        input: String?,
+        expects error: InputValidationError?
+    ) async throws {
+        try assertValidate(
+            rule: .url,
+            input: input,
+            expects: error
+        )
+    }
 #endif
     
 }
@@ -203,6 +287,8 @@ private extension ValidateInputUseCaseTests {
 // MARK: - Constants
 
 private extension Input {
+    /// A list of inputs to validate against a camel-case validation rule.
+    static let inputsCamelCase: [String] = ["SampleApp", "Sample4pp", "SampleApp1", "SampleApp🚀", "Sample App", "Sample-App", "Sample_App"]
     /// A list of inputs to validate against the not empty validation rule.
     static let inputsNotEmpty: [String] = ["Something", .empty]
     /// A list of inputs to validate against the not nil validation rule.
@@ -213,9 +299,15 @@ private extension Input {
     static let inputsSecureConsumerSecret: [String] = ["aAbBcCdDeEfFgGhHiIjJkKlLmMnNoOpP", "aAbBcCdDeEfFgGhHiIjJkKlLmMnNoO", "aAbBcCdDeEfFgGhHiIjJkKlLmMnNoOpPqQ", "a4bBcCdDe3fFg6hH1IjJkK1LmMnNo0p9"]
     /// A list of inputs to validate against the secure (user token) validation rule.
     static let inputsSecureUserToken: [String] = ["aAbBcCdDeEfFgGhHiIjJkKlLmMnNoOpPqQrRsStT", "aAbBcCdDeEfFgGhHiIjJkKlLmMnNoOpPqQrRsS", "aAbBcCdDeEfFgGhHiIjJkKlLmMnNoOpPqQrRsStTuU", "a4bBcCdDe3fFg6hH1IjJkK1LmMnNo0p9qQrRs5t7"]
+    /// A list of inputs to validate against the semantic version validation rule.
+    static let inputsSemanticVersion: [String] = ["0.0.4","1.2.3","10.20.30","1.1.2-prerelease+meta","1.1.2+meta","1.1.2+meta-valid","1.0.0-alpha","1.0.0-beta","1.0.0-alpha.beta","1.0.0-alpha.beta.1","1.0.0-alpha.1","1.0.0-alpha0.valid","1.0.0-alpha.0valid","1.0.0-alpha-a.b-c-somethinglong+build.1-aef.1-its-okay","1.0.0-rc.1+build.1","2.0.0-rc.1+build.123","1.2.3-beta","10.2.3-DEV-SNAPSHOT","1.2.3-SNAPSHOT-123","1.0.0","2.0.0","1.1.7","2.0.0+build.1848","2.0.1-alpha.1227","1.0.0-alpha+beta","1.2.3----RC-SNAPSHOT.12.9.1--.12+788","1.2.3----R-S.12.9.1--.12+meta","1.2.3----RC-SNAPSHOT.12.9.1--.12","1.0.0+0.build.1-rc.10000aaa-kk-0.1","99999999999999999999999.999999999999999999.99999999999999999","1.0.0-0A.is.legal","1","1.2","1.2.3-0123","1.2.3-0123.0123","1.1.2+.123","+invalid","-invalid","-invalid+invalid","-invalid.01","alpha","alpha.beta","alpha.beta.1","alpha.1","alpha+beta","alpha_beta","alpha.","alpha..","beta","1.0.0-alpha_beta","-alpha.","1.0.0-alpha..","1.0.0-alpha..1","1.0.0-alpha...1","1.0.0-alpha....1","1.0.0-alpha.....1","1.0.0-alpha......1","1.0.0-alpha.......1","01.1.1","1.01.1","1.1.01","1.2","1.2.3.DEV","1.2-SNAPSHOT","1.2.31.2.3----RC-SNAPSHOT.12.09.1--..12+788","1.2-RC-SNAPSHOT","-1.0.3-gamma+b7718","+justmeta","9.8.7+meta+meta","9.8.7-whatever+meta+meta","99999999999999999999999.999999999999999999.99999999999999999----RC-SNAPSHOT.12.09.1--------------------------------..12"]
+    /// A list of inputs to validate against the URL validation rule.
+    static let inputsURL: [String] = ["https://www.google.com", "http://www.google.com", "https://google.com/q=search", "http://google.com/q=search", "3333-768-0948", "1133.168.0248", "7678*999-8978", "httpq://google.com/q=search", "www.google.com", "www.google.com/?search=qppoao", "www . google.com/?search=qppoao", "https : //google.com/q=search", "htt://www.google.com", "://www.google.com", .empty]
 }
 
 private extension Output {
+    /// A list of expected input validation errors to be thrown after validating inputs against the camel-case validation rule.
+    static let inputsCamelCase: [InputValidationError?] = [nil, nil, nil, .inputNotCamelCase, .inputNotCamelCase, .inputNotCamelCase, .inputNotCamelCase]
     /// A list of expected input validation errors to be thrown after validating inputs against the not empty validation rule.
     static let inputsNotEmpty: [InputValidationError?] = [nil, .inputIsEmpty]
     /// A list of expected input validation errors to be thrown after validating inputs against the not nil validation rule.
@@ -226,4 +318,8 @@ private extension Output {
     static let inputsSecureConsumerSecret: [InputValidationError?] = [nil, .inputNotConsumerSecret, .inputNotConsumerSecret, .inputNotConsumerSecret]
     /// A list of expected input validation errors to be thrown after validating inputs against the secure (user token) validation rule.
     static let inputsSecureUserToken: [InputValidationError?] = [nil, .inputNotUserToken, .inputNotUserToken, .inputNotUserToken]
+    /// A list of expected input validation errors to be thrown after validating inputs against the semantic version validation rule.
+    static let inputsSemanticVersion: [InputValidationError?] = [nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion]
+    /// A list of expected input validation errors to be thrown after validating inputs against the URL validation rule.
+    static let inputsURL: [InputValidationError?] = [nil, nil, nil, nil, .inputNotURL, .inputNotURL, .inputNotURL, .inputNotURL, .inputNotURL, .inputNotURL, .inputNotURL, .inputNotURL, .inputNotURL, .inputNotURL, .inputNotURL]
 }