remove duplication in REST API client HTTP verb methods
remove duplication in REST API client HTTP verb methods

fixes #343

geometalab/osmaxx-frontend,geometalab/osmaxx,geometalab/osmaxx-frontend,geometalab/osmaxx,geometalab/drf-utm-zone-info,geometalab/drf-utm-zone-info,geometalab/osmaxx,geometalab/osmaxx-frontend,geometalab/osmaxx-frontend,geometalab/osmaxx