Implemented project delete endpoint for REST API.
Added project usage status check service method to indicate if project can be deleted.
Updated project invoice status check method to indicate if project can be deleted.
Change-Id: I57dc96efb072517144252001ab5405446c9cdeb4
Implemented new service method for generating API keys.
Implemented new endpoint.
Improved multiple endpoint groups handling.
Change-Id: Iba26fbf9123707b5b4c2d5e8c5a35d507404f24a
Added documentation.
Replaced PUT request with POST request.
Added inline param support for PATCH request.
Replaced unix timestamps handling with RFC-3339 timestampts handling.
Added 'Bearer' method requirement for Authorization header.
Change-Id: I4faa3864051dd18826c2c583ada53666d4aaec44