terms and conditions agreement

[loomis]

To manage the terms and conditions agreement process, implement the following:

• Add a boolean field ("agreed"?) to the user resource.
• Add the same boolean field to the user template resources to require agreement when registering.
• Create a callback that allows a user to indicate agreement with the terms and conditions.

Any login attempt without this field being set will return a 401 response, location header to an agreement callback, and a message with a link to the terms and conditions.

As the UI uses the API, this will also work there. However, the response may need to be treated specially to have a reasonable browser workflow.