feat(ai): add file translation methods support

[innomaxx]

Closes #360

[Copilot]

Pull request overview

Adds Crowdin AI File Translation endpoint support to the AI executor layer, along with unit tests and test resources, enabling SDK consumers to start/cancel file translation jobs and download results.

Changes:

• Introduces request/response models for AI file translation jobs (AiFileTranslationsRequest, AiFileTranslationsStatus, AiFileTranslationsStage).
• Extends IAiApiExecutor / AiApiExecutor with methods to start a job, fetch status, cancel, and download translated artifacts.
• Adds unit tests plus new .resx fixtures and a shared download-link assertion helper.

Reviewed changes

Copilot reviewed 10 out of 12 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
tests/Crowdin.Api.UnitTesting/Tests/AI/AiFileTranslationsTests.cs	Adds unit tests covering AI file translation start/status/cancel/download APIs.
tests/Crowdin.Api.UnitTesting/Resources/Common.resx	Adds shared download link JSON fixture.
tests/Crowdin.Api.UnitTesting/Resources/Common.Designer.cs	Strongly-typed accessor for Common.resx.
tests/Crowdin.Api.UnitTesting/Resources/AI_FileTranslations.resx	Adds request/response JSON fixtures for AI file translation endpoints.
tests/Crowdin.Api.UnitTesting/Resources/AI_FileTranslations.Designer.cs	Strongly-typed accessor for AI_FileTranslations.resx.
tests/Crowdin.Api.UnitTesting/Crowdin.Api.UnitTesting.csproj	Wires new .resx files and designers into the test project.
tests/Crowdin.Api.UnitTesting/CommonResponsesAssertUtils.cs	Adds shared assertions for DownloadLink responses.
src/Crowdin.Api/AI/IAiApiExecutor.cs	Adds new public executor methods for AI file translation workflows.
src/Crowdin.Api/AI/AiFileTranslationsStatus.cs	Adds response model for file translation job status.
src/Crowdin.Api/AI/AiFileTranslationsStage.cs	Adds enum for job stage values.
src/Crowdin.Api/AI/AiFileTranslationsRequest.cs	Adds request model for starting AI file translations.
src/Crowdin.Api/AI/AiApiExecutor.cs	Implements the new AI file translation endpoints.

Files not reviewed (2)

• tests/Crowdin.Api.UnitTesting/Resources/AI_FileTranslations.Designer.cs: Language not supported
• tests/Crowdin.Api.UnitTesting/Resources/Common.Designer.cs: Language not supported

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[Copilot]

DownloadTranslatedFile is missing the [PublicAPI] attribute, while other public methods in this executor are consistently annotated. For consistency (and to match the other AI endpoints), add [PublicAPI] to this method as well.

Suggested change

	/// </summary>
	/// </summary>
	[PublicAPI]

[Copilot]

Method name AiFileTranslations(...) reads like a noun/resource name rather than an action, which is inconsistent with the rest of IAiApiExecutor (e.g., GenerateAiReport, TranslateStrings, DownloadAiReport). Consider renaming this to a verb-based name (e.g., StartFileTranslation / TranslateFile) so the public API is clearer and more consistent.

[Copilot]

Implementation method name AiFileTranslations(...) is noun-like and inconsistent with the executor's other verb-based method names. If you rename the interface method for consistency/clarity, update this implementation accordingly to keep the public API self-explanatory.

Suggested change

	public async Task<AiFileTranslationsStatus> AiFileTranslations(long? userId, AiFileTranslationsRequest request)
	{
	string url = AddUserIdIfAvailable(userId, "/ai/file-translations");
	CrowdinApiResult result = await _apiClient.SendPostRequest(url, request);
	return _jsonParser.ParseResponseObject<AiFileTranslationsStatus>(result.JsonObject);
	}
	public async Task<AiFileTranslationsStatus> StartFileTranslations(long? userId, AiFileTranslationsRequest request)
	{
	string url = AddUserIdIfAvailable(userId, "/ai/file-translations");
	CrowdinApiResult result = await _apiClient.SendPostRequest(url, request);
	return _jsonParser.ParseResponseObject<AiFileTranslationsStatus>(result.JsonObject);
	}
	Task<AiFileTranslationsStatus> IAiApiExecutor.AiFileTranslations(long? userId, AiFileTranslationsRequest request)
	{
	return StartFileTranslations(userId, request);
	}

[Copilot]

Assert_DownloadLink parameter name expectedDownloadLink is misleading because the method asserts against the actual response value passed in by callers. Rename it to something like downloadLink/actualDownloadLink to make intent clearer.

Suggested change

	public static void Assert_DownloadLink(DownloadLink? expectedDownloadLink)
	{
	ArgumentNullException.ThrowIfNull(expectedDownloadLink);
	Assert.Equal("https://test.com", expectedDownloadLink.Url);
	Assert.Equal(DateTimeOffset.Parse("2019-09-20T10:31:21+00:00"), expectedDownloadLink.ExpireIn);
	public static void Assert_DownloadLink(DownloadLink? downloadLink)
	{
	ArgumentNullException.ThrowIfNull(downloadLink);
	Assert.Equal("https://test.com", downloadLink.Url);
	Assert.Equal(DateTimeOffset.Parse("2019-09-20T10:31:21+00:00"), downloadLink.ExpireIn);