Upgrade Doorkeeper from 3.1.0 to 4.0.0.
Includes Rails 5 support and various bug fixes. Working toward #14286 (closed).
Changelog: https://github.com/doorkeeper-gem/doorkeeper/blob/master/NEWS.md#400
cc: @rspeicher
Includes Rails 5 support and various bug fixes. Working toward #14286 (closed).
Changelog: https://github.com/doorkeeper-gem/doorkeeper/blob/master/NEWS.md#400
cc: @rspeicher