Patch inactive user issue in V2 API

[momo3404]

Changes proposed in this PR:

• Add authorize_resource_owner function to V2 base_api_controller that checks if user is active and present before authorization.
• Add render_error function to V2 API.
• Create base_controller_spec for V2 base_api_controller.
• Note for reviewers: This PR changes the error response shape for the v2 API — message has been removed and replaced with errors. Also worth flagging: the type changed too, not just the field name. message was an array of strings; errors is a plain string.

// Before
{ "code": 500, "message": ["There was a problem in the server."], "items": [] }

// After
{ "code": 500, "items": [], "errors": "There was a problem in the server." }

This is a breaking change for any consumer reading message off v2 error responses.

[aaronskiba]

One test is breaking and it must be because you are calling render_error, but this repo does not yet define it (DMP Assistant added it here: portagenetwork@b1bd290).