Ensure each Apinf user has one and only one associated API Umbrella user

[bajiat]

Currently, our Admin dashboard allows creation of new API Umbrella users. However, API Umbrella users should be created when Apinf user is created rather than in a separate process.

Definition of done

• Remove API Umbrella user widget from Admin dashboard.
• Create collection hook to create new API Umbrella user when creating Apinf user.
• Make sure Apinf users are only linked to one API Umbrella user.

[brylie]

I have removed the form widget. The schema only allows one apiUmbrellaId value per user.

[brylie]

We verified that the user is being created and cross-linked in our accounts.coffee#52-72. We need a new task to unit test the aforementioned lines.

[brylie]

I created an issue (#202) to unit test the accounts.coffee.