[Feature] Communications (#4)

This PR constains the work done to define the necessary protocols and enumerations to start defining remote API service as well as an implementation of the `URLProtocol` to mock requests and responses when using the `URLSession` to make remote calls.

To provide further details about this work:
- [x] declared the `Communications` library in the `Package` file;
- [x] defined the minimum Apple platform versions in the `Package` file to support the async/await feature;
- [x] defined the `HTTPRequestMethod` and `HTTPResponseCode` public enumerations;
- [x] defined the `Endpoint` and `Client` public protocols;
- [x] implemented the internal `MakeURLRequestUseCase` use case;
- [x] implemented the `MockURLProtocol` class that mocks requests and responses on `URLSession` instances;
- [x] started writing and updating the `README` file.

Co-authored-by: Javier Cicchelli <javier@rock-n-code.com>
Reviewed-on: #4

Tests/Communications/Use Cases/MakeURLRequestUseCaseTests.swift

@@ -0,0 +1,118 @@
+//
+//  MakeURLRequestUseCaseTests.swift
+//  CommunicationsTests
+//
+//  Created by Javier Cicchelli on 10/04/2023.
+//  Copyright © 2023 Röck+Cöde. All rights reserved.
+//
+
+import Communications
+import Foundation
+import XCTest
+
+final class MakeURLRequestUseCaseTests: XCTestCase {
+
+    // MARK: Properties
+    
+    private let makeURLRequest = MakeURLRequestUseCase()
+
+    // MARK: Test cases
+    
+    func test_withEndpoint_initialisedByDefault() throws {
+        // GIVEN
+        let endpoint = TestEndpoint()
+        
+        // WHEN
+        let result = try makeURLRequest(endpoint: endpoint)
+        
+        // THEN
+        XCTAssertNotNil(result)
+        XCTAssertEqual(result.url?.absoluteString, "http://www.something.com/path/to/endpoint")
+        XCTAssertEqual(result.httpMethod, HTTPRequestMethod.get.rawValue)
+        XCTAssertEqual(result.allHTTPHeaderFields, [:])
+        XCTAssertNil(result.httpBody)
+    }
+    
+    func test_withEndpoint_initialisedWithPort() throws {
+        // GIVEN
+        let endpoint = TestEndpoint(port: 8080)
+        
+        // WHEN
+        let result = try makeURLRequest(endpoint: endpoint)
+        
+        // THEN
+        XCTAssertNotNil(result)
+        XCTAssertEqual(result.url?.absoluteString, "http://www.something.com:8080/path/to/endpoint")
+        XCTAssertEqual(result.httpMethod, HTTPRequestMethod.get.rawValue)
+        XCTAssertEqual(result.allHTTPHeaderFields, [:])
+        XCTAssertNil(result.httpBody)
+    }
+    
+    func test_withEndpoint_initialisedWithHeaders() throws {
+        // GIVEN
+        let endpoint = TestEndpoint(headers: [
+            "aHeader": "aValueForHead",
+            "someOtherHeader": "someValueForOtherHeader"
+        ])
+        
+        // WHEN
+        let result = try makeURLRequest(endpoint: endpoint)
+        
+        // THEN
+        XCTAssertNotNil(result)
+        XCTAssertEqual(result.url?.absoluteString, "http://www.something.com/path/to/endpoint")
+        XCTAssertEqual(result.httpMethod, HTTPRequestMethod.get.rawValue)
+        XCTAssertEqual(result.allHTTPHeaderFields, [
+            "aHeader": "aValueForHead",
+            "someOtherHeader": "someValueForOtherHeader"
+        ])
+        XCTAssertNil(result.httpBody)
+    }
+    
+    func test_withEndpoint_initialisedWithBody() throws {
+        // GIVEN
+        let data = "This is some data for a body of a request".data(using: .utf8)
+        let endpoint = TestEndpoint(body: data)
+        
+        // WHEN
+        let result = try makeURLRequest(endpoint: endpoint)
+        
+        // THEN
+        XCTAssertNotNil(result)
+        XCTAssertEqual(result.url?.absoluteString, "http://www.something.com/path/to/endpoint")
+        XCTAssertEqual(result.httpMethod, HTTPRequestMethod.get.rawValue)
+        XCTAssertEqual(result.allHTTPHeaderFields, [:])
+        XCTAssertEqual(result.httpBody, data)
+        XCTAssertNotNil(data)
+    }
+
+}
+
+// MARK: - TestEndpoint
+
+private struct TestEndpoint: Endpoint {
+
+    // MARK: Properties
+    
+    let scheme: String = "http"
+    let host: String = "www.something.com"
+    let path: String = "/path/to/endpoint"
+    let method: HTTPRequestMethod = .get
+    
+    var port: Int?
+    var headers: [String : String]
+    var body: Data?
+
+    // MARK: Initialisers
+    
+    init(
+        port: Int? = nil,
+        headers: [String : String] = [:],
+        body: Data? = nil
+    ) {
+        self.port = port
+        self.body = body
+        self.headers = headers
+    }
+
+}