Add moderation API (#9387)

app/controllers/admin/accounts_controller.rb

app/controllers/api/v1/admin/account_actions_controller.rb

app/controllers/api/v1/admin/accounts_controller.rb

app/controllers/api/v1/admin/reports_controller.rb

app/models/account.rb

app/models/account_filter.rb

app/models/concerns/user_roles.rb

app/models/report.rb

app/models/report_filter.rb

app/models/user.rb

app/serializers/rest/admin/account_serializer.rb

app/serializers/rest/admin/report_serializer.rb

config/initializers/doorkeeper.rb

config/locales/doorkeeper.en.yml

config/routes.rb

...ntrollers/api/v1/admin/account_actions_controller_spec.rb

spec/controllers/api/v1/admin/accounts_controller_spec.rb

spec/controllers/api/v1/admin/reports_controller_spec.rb