test: simplify unit tests setup for command and callback handlers

[isSerge]

Closes #81

• Create TestHarness utility struct with helper methods
• Move unit tests for handlers to dedicated command and callback modules

[Copilot]

Pull Request Overview

Refactors unit tests for bot handlers to use a TestHarness utility and moves tests closer to the code they test. The PR eliminates a large central test file in favor of dedicated test modules within each handler module.

• Creates a TestHarness utility struct with helper methods to simplify test setup
• Moves command handler tests from centralized location to dedicated add.rs module
• Moves callback handler tests to their respective modules (view_repo.rs, view_labels.rs, remove.rs, list.rs)

Reviewed Changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
src/bot_handler/tests.rs	Removes entire centralized test file (1008 lines deleted)
src/bot_handler/test_helpers.rs	Adds new test utility module with TestHarness and helper functions
src/bot_handler/mod.rs	Updates module imports and adds Display trait for Command enum
src/bot_handler/commands/add.rs	Adds comprehensive test module for add command functionality
src/bot_handler/callbacks/view_repo.rs	Adds test module for repository detail view callbacks
src/bot_handler/callbacks/view_labels.rs	Adds test module for label view and toggle callbacks
src/bot_handler/callbacks/remove.rs	Adds test module for repository removal callbacks
src/bot_handler/callbacks/list.rs	Adds test module for repository list callbacks

[Copilot]

The multi-line string literal should be properly formatted. Consider using a single line or proper indentation to avoid confusion about the actual error message content.

Suggested change

	let limit_error_msg = "You have reached the maximum limit of 10
	repositories.";
	let limit_error_msg = "You have reached the maximum limit of 10 repositories.";

[Copilot]

The multi-line string literal should be properly formatted. Consider using a single line or proper indentation to maintain consistency with the test data structure.

Suggested change

	"{url_new} {url_tracked} {url_notfound} {url_invalid} {url_gh_error}
	{url_add_error}"
	"{url_new}\n\
	{url_tracked}\n\
	{url_notfound}\n\
	{url_invalid}\n\
	{url_gh_error}\n\
	{url_add_error}"