A command that allows the user to attach a file to a specific review request.

Args: rb attach <request_id> <path/to/file>
Options: --description (caption), --filename (custom filename)

Tried the following on dev server, all of which were successful:

rb attach <request_id> <path/to/file>
rb attach <request_id> <path/to/file> --description='some desc'
rb attach <request_id> <path/to/file> --filename='custom filename'
rb attach <request_id> <path/to/file> --description='some desc' --filename='custom filename'

rb attach <invalid_request_id>
rb patch <invalid_request_id> <invalid/path/to/file>
rb attach <invalid/path/to/file>

Retested with rb-general (removal of extra options)