Add tests and separate from class validation merge methods

[aneuwald-ctw]

User-Facing Changes
Added validation for merging MCAP files and introduced unit tests for the load-multiple-mcaps story.

Description

• Refactored merging and validation logic into a separate file for better testability.
• Added unit tests for mergeAsyncIterators and MultiIterableSource.
• Fixed a typo in the Initialization interface (previously Initalization).

Checklist

• The web version was tested and it is running ok
• The desktop version was tested and it is running ok
• This change is covered by unit tests
• Files constants.ts, types.ts and *.style.ts have been checked and relevant code snippets have been relocated

[aneuwald-ctw]

I don't understand why the MultiIterableSource.ts is considered as 0% tested. I believe that it is something related to how sonar is configured. I suggest to merge it and check when we point to merge to main if it will be considered.

[gabriela-almeida-ctw]

suggestion: This branching should be tested. Since this is a private method, I would suggest testing where its behaviour is expected. Therefore, during initialization.
Tests would look something like the following:

it("source type is file", async () => {
    dataSource = {
      type: "files",
      files: [new Blob(), new Blob()],
    };
    const multiSource = new MultiIterableSource(dataSource, mockSourceConstructor);
    await multiSource.initialize();

    expect(mockSourceConstructor).toHaveBeenCalledWith(expect.objectContaining({ type: "file" }));
  });

  it("source type is url", async () => {
    dataSource = {
      type: "urls",
      urls: ["my.url/"],
    };
    const multiSource = new MultiIterableSource(dataSource, mockSourceConstructor);
    await multiSource.initialize();

    expect(mockSourceConstructor).toHaveBeenCalledWith(expect.objectContaining({ type: "url" }));
  });

[luluiz]

done

[sonarqubecloud]

Quality Gate failed

Failed conditions
77.5% Coverage on New Code (required ≥ 80%)

See analysis details on SonarQube Cloud