Allow configuring scope

Drupal's GitLab is giving me some trouble at the moment and I'm not able to change it, but the 1.x MR should be targeting the 1.x branch.

Thanks for this, here is a backport which I require for 7.x-1.x

I think this would be a great improvement, but I think there's some work needed on the PR.

When opening any existing clients, we see the error:
Warning: Undefined array key "scopes" in Drupal\openid_connect_windows_aad\Plugin\OpenIDConnectClient\WindowsAad->buildConfigurationForm() (line 269 of modules/contrib/openid_connect_windows_aad/src/Plugin/OpenIDConnectClient/WindowsAad.php).

I think this is because we'll need an update hook to set the configuration (even as empty) on any existing clients.

I think we also need to add the 'scopes' as an item in the schema.yml file.

As a headstart, you could take a look at how custom scopes were implemented in the 'generic' provider of the parent module: https://git.drupalcode.org/project/openid_connect/-/commit/21bd2ae21b640...