Add REST API invited groups in a group

app/finders/concerns/namespaces/groups_filter.rb

app/finders/namespaces/groups/invited_groups_finder.rb

app/finders/namespaces/groups/shared_groups_finder.rb

app/helpers/application_settings_helper.rb

app/models/application_setting.rb

app/models/application_setting_implementation.rb

...idators/json_schemas/application_setting_rate_limits.json

...s/admin/application_settings/_groups_api_limits.html.haml

doc/api/groups.md

lib/api/groups.rb

lib/gitlab/application_rate_limiter.rb

spec/features/admin/admin_settings_spec.rb

spec/finders/namespaces/groups/invited_groups_finder_spec.rb

spec/helpers/application_settings_helper_spec.rb

spec/models/application_setting_spec.rb

spec/requests/api/groups_spec.rb