MAAS accepts user-data in different formats depending on the UI or API

Both the UI and API accept user-data however they each require a different format. The UI requires user-data to be in plain text and will silently fail if base64 encoded data is given. The API requires user-data to be base64 encoded and fails with an exception if plain text is given.

MAAS should accept either plain text or base64 encoded data on both the API and UI. The backend should be smart enough to know if the user uploaded plain text and automatically convert it to base64 as needed.