v5.2.0.rc3

• [#1298] Slice strong params so doesn't error with Rails forms.
• [#1300] Limiting access to attributes of pre_authorization.
• [#1296] Adding client_id to strong parameters.
• [#1293] Move ar specific redirect uri validator to ar orm directory.
• [#1288] Allow to pass attributes to the Doorkeeper::OAuth::PreAuthorization#as_json method to customize
  the PreAuthorization response.
• [#1286] Add ability to customize grant flows per application (OAuth client) (#1245 , #1207)
• [#1283] Allow to customize base class for Doorkeeper::ApplicationMetalController (new configuration
  option called base_metal_controller (fix #1273).
• [#1277] Prevent requested scope be empty on authorization request, handle and add description for invalid request.