OAuth flows should be included in a Service "only" settings view

Currently the OAuth flows that can be enabled per Service are included in the configuration page which includes all other proxy config settings. This is confusing for 2 reasons:

1. The settings are actually Service related
2. The settings/changes are only propagated when updating the staging configuration

I would recommend to move these settings to the Integration settings view. When choosing the OpenID Connect authentication mode the user can also set the list of allowed flows and save them accordingly. In case this is the first time the OpenID Connect mode is being set then the staging config needs to be updated anyway to set the authentication_mode: oidc in the proxy config. However, if it's just an update to the allowed flows then they do not need to be propagated any further.