Fix establish_connection configuration for custom defined models

CHANGELOG.md

@@ -8,6 +8,7 @@ User-visible changes worth mentioning.
 ## master
 
 - [#PR ID] Add your PR description here.
+- [#1472] Fix `establish_connection` configuration for custom defined models.
 - [#1471] Add support for Ruby 3.0.
 - [#1469] Check if `redirect_uri` exists.
 - [#1465] Memoize nil doorkeeper_token.

lib/doorkeeper/config.rb

@@ -29,6 +29,8 @@ def configure(&block)
       @config
     end
 
+    # @return [Doorkeeper::Config] configuration instance
+    #
     def configuration
       @config || (raise MissingConfiguration)
     end

lib/doorkeeper/orm/active_record.rb

@@ -20,9 +20,8 @@ def self.initialize_models!
           require "doorkeeper/orm/active_record/access_token"
           require "doorkeeper/orm/active_record/application"
 
-          if Doorkeeper.config.active_record_options[:establish_connection]
+          if (options = Doorkeeper.config.active_record_options[:establish_connection])
             Doorkeeper::Orm::ActiveRecord.models.each do |model|
-              options = Doorkeeper.config.active_record_options[:establish_connection]
               model.establish_connection(options)
             end
           end
@@ -51,9 +50,9 @@ def self.lazy_load(&block)
 
       def self.models
         [
-          Doorkeeper::AccessGrant,
-          Doorkeeper::AccessToken,
-          Doorkeeper::Application,
+          Doorkeeper.config.access_grant_model,
+          Doorkeeper.config.access_token_model,
+          Doorkeeper.config.application_model,
         ]
       end
     end