v5.1.0.rc1

• [#1188] Use params instead of request.POST in tokens controller (fixes #1183).
• [#1182] Fix loopback IP redirect URIs to conform with RFC8252, p. 7.3 (fixes #1170).
• [#1179] Authorization Code Grant Flow without client id returns invalid_client error.
• [#1177] Allow to limit scopes for certain grant_types
• [#1176] Fix test factory support for factory_bot_rails
• [#1175] Internal refactor: use scopes_string inside scopes.
• [#1168] Allow optional hashing of tokens and secrets.
• [#1164] Fix error when root_path is not defined.
• [#1162] Fix enforce_content_type for requests without body.