Endpoint to deal with a user's admin status

[Stephen Morrison]

1. Make a user an admin

Method: PUT
Body (JSON):

• user ID

Response:

• status code 401 if the user doesn't exist
• status code 200 if they were successfully made an admin

2. Make a user not an admin

Method: PUT
Body (JSON):

• user ID
• password

Response:

• status code 401 if the user's password is invalid or the user is not valid
• status code 200 if the user's admin status was successfully changed

[cesarl88]

Implemented and tested in the test server