[API] Deprecate unnecessary /update_role/ API endpoint

[john-bodley]

This PR removes the /update_role/ API endpoint which it seems was added specifically for an Airbnb use case. The endpoint appends users (new or existing) to a role which is invoked for syncing external permissions. The issue with this approach is it merely grants permissions and never revokes.

This use case seems very tailored, and thus rather than adding additional API endpoints to removes users it seems a more prudent approach would be to leverage the FAB REST API. Specifically the same functionality can be achieved via something of the form,

import request

# Create a new user.
requests.put(
    'http://localhost:8088/users/api/create',
    data={
        'username': 'john_doe',		
        'first_name': 'John',		
        'last_name': 'Doe',		
        'email': '[email protected]',
    },
)

# Set the list of users associated with the 'Alpha' role.
request.put(
    'http://localhost:8088/roles/api/update/3',
    data={'name': 'Alpha', 'user': [1, 2, 3]},
)

which defines the set of users (via primary key) associated with the Alpha role. This method provides the ability to add or remove users since the the user list defines the complete set of users associated with said role.

to: @mistercrunch

[mistercrunch]

In general we try to not ship backwards incompatible changes, but I'm guessing this is only used at Airbnb and we're pre 1.0, so let's turn this endpoint off.