Support Logout and OIDC Metadata
Grant js should allow us to logout of the OAuth provider by forwarding a request to the OAuth providers logout url.

Also OIDC providers should have a metadata endpoint:
https://docs.microsoft.com/en-us/azure/active-directory/develop/v1-protocols-openid-connect-code#openid-connect-metadata-document

Similarly to grant-profile we should be able to fetch the correct url using the metadata and a map of logout urls to providers.