[diego] Renamed member's member_info API method to show
[diego] Filter member fields on response

Instead of using the default JSON serialization for the User object,
updated controller to return a projection with only the fields relevant
to the movement site
[diego] Filter member's info from response on member creation

Instead of using the default JSON serialization for the User object,
updated controller to return a projection with only the fields relevant
to the movement site
[diego] Remove 'success' field from JSON responses

To make the API more RESTful, removed success field from JSON responses
and verified the correct status code is returned on each response
[diego] Update take_action response status code

Updated the HTTP response's status code to 400 if member already took
action and 500 if any other error occurs