Root folder creation (#2)

This PR contains the work done to create the root folder of a new project when executing the _colibri_ executable. In addition, some other work has been done:

* added the `ArgumentParser` package dependency to the package;
* implemented the `FileService` service in the _library_ target;
* implemented the `CreateRootFolderTask` task in the _library_ target;
* removed some unnecessary comments and boilerplate code;

Reviewed-on: #2
Co-authored-by: Javier Cicchelli <javier@rock-n-code.com>
Co-committed-by: Javier Cicchelli <javier@rock-n-code.com>

Tests/Library/Cases/Services/FileServiceTests.swift

@@ -0,0 +1,154 @@
+import ColibriLibrary
+import Foundation
+import Testing
+
+struct FileServiceTests {
+    
+    // MARK: Properties
+    
+    private let spy = FileServiceSpy()
+
+    // MARK: Properties tests
+
+    @Test func currentFolder() async {
+        // GIVEN
+        let url: URL = .someCurrentFolder
+        
+        let service = FileServiceMock(currentFolder: url)
+
+        // WHEN
+        let folder = await service.currentFolder
+
+        // THEN
+        #expect(folder == url)
+        #expect(folder.isFileURL == true)
+    }
+    
+    // MARK: Functions
+    
+    @Test(arguments: [URL.someNewFolder, .someNewFile])
+    func createFolder(with url: URL) async throws {
+        // GIVEN
+        let service = FileServiceMock(
+            currentFolder: .someCurrentFolder,
+            action: .createFolder(url),
+            spy: spy
+        )
+
+        // WHEN
+        try await service.createFolder(at: url)
+        
+        // THEN
+        #expect(spy.isCreateFolderCalled == true)
+        #expect(spy.urlCalled == url)
+    }
+    
+    @Test(arguments: zip([URL.someExistingFolder, .someExistingFile, .someRandomURL],
+                         [FileServiceError.urlAlreadyExists, .urlAlreadyExists, .urlNotFileURL]))
+    func createFolder(
+        with url: URL,
+        throws error: FileServiceError
+    ) async throws {
+        // GIVEN
+        let service = FileServiceMock(
+            currentFolder: .someCurrentFolder,
+            action: .error(error),
+            spy: spy
+        )
+
+        // WHEN
+        // THEN
+        await #expect(throws: error) {
+            try await service.createFolder(at: url)
+        }
+
+        #expect(spy.isCreateFolderCalled == false)
+        #expect(spy.urlCalled == nil)
+    }
+    
+    @Test(arguments: [URL.someNewFolder, .someNewFile])
+    func delete(with url: URL) async throws {
+        // GIVEN
+        let service = FileServiceMock(
+            currentFolder: .someCurrentFolder,
+            action: .delete(url),
+            spy: spy
+        )
+
+        // WHEN
+        try await service.delete(at: url)
+
+        // THEN
+        #expect(spy.isDeleteCalled == true)
+        #expect(spy.urlCalled == url)
+    }
+    
+    @Test(arguments: zip([URL.someNewFolder, .someNewFile, .someRandomURL],
+                         [FileServiceError.urlNotExists, .urlNotExists, .urlNotFileURL]))
+    func delete(
+        with url: URL,
+        throws error: FileServiceError
+    ) async throws {
+        // GIVEN
+        let service = FileServiceMock(
+            currentFolder: .someCurrentFolder,
+            action: .error(error),
+            spy: spy
+        )
+        
+        // WHEN
+        // THEN
+        await #expect(throws: error) {
+            try await service.delete(at: url)
+        }
+
+        #expect(spy.isDeleteCalled == false)
+        #expect(spy.urlCalled == nil)
+    }
+    
+    @Test(arguments: zip([URL.someExistingFolder, .someExistingFile, .someNewFolder, .someNewFile],
+                         [true, true, false, false]))
+    func exists(
+        with url: URL,
+        expects outcome: Bool
+    ) async throws {
+        // GIVEN
+        let service = FileServiceMock(
+            currentFolder: .someCurrentFolder,
+            action: .exists(url, outcome),
+            spy: spy
+        )
+
+        // WHEN
+        let result = try await service.exists(at: url)
+        
+        // THEN
+        #expect(result == outcome)
+
+        #expect(spy.isExistsAtCalled == true)
+        #expect(spy.urlCalled == url)
+    }
+    
+    @Test(arguments: zip([URL.someRandomURL], [FileServiceError.urlNotFileURL]))
+    func exists(
+        with url: URL,
+        throws error: FileServiceError
+    ) async throws {
+        // GIVEN
+        let service = FileServiceMock(
+            currentFolder: .someCurrentFolder,
+            action: .error(error),
+            spy: spy
+        )
+
+        // WHEN
+        // THEN
+        await #expect(throws: error) {
+            try await service.exists(at: url)
+        }
+        
+        #expect(spy.isExistsAtCalled == false)
+        #expect(spy.urlCalled == nil)
+    }
+
+}