Kanboard API returns int (ID) on success and false (bool) on failure
for create operations. Add IntOrFalse type that handles both cases
and update CreateTask, CreateComment, CreateTag, CreateTaskFile, and
CreateTaskLink to use it.
- GetAllComments: retrieve all comments for a task
- GetComment: retrieve single comment by ID
- CreateComment: create comment and return the created comment
- UpdateComment: update comment content
- RemoveComment: delete a comment
- TaskScope.GetComments and AddComment for fluent API
- Returns ErrCommentNotFound when appropriate
- Comprehensive test coverage
