Add Backend support for Location Removal Requests

• Adds model class LocationRemovalRequest, encapsulating the reporter's email, reason, location_id & timestamp

  • to_dict produces output to be stored in the database, from_dict to read from the database
  • to_geojson takes the Location object that matches the stored location_id. It outputs a GeoJSON string, which includes the removal request's attributes inside the properties field

• Adds the following functions to the Locations REST service

  • add_removal_request - storing a given removal request object to the locations_requests MongoDB collection
  • delete_removal_request
  • get_removal_requests_as_geojson
    1. retrieves all LocationRemovalRequest objects and associated Location objects from the DB
    2. automatically removes removal requests when there is no matching Location object
    3. returns a list of GeoJSON strings for the frontend, including Location and removal request details.

• Refactors logger calls to use printf strings