Use user.FullName in Oauth2 id_token response

This makes `/#/oauth/authorize` behave the same way as the
`/#/oauth/userinfo` endpoint.

services/oauth2_provider/access_token.go

@@ -148,7 +148,7 @@ func NewAccessTokenResponse(ctx context.Context, grant *auth.OAuth2Grant, server
 			Nonce: grant.Nonce,
 		}
 		if grant.ScopeContains("profile") {
-			idToken.Name = user.GetDisplayName()
+			idToken.Name = user.FullName
 			idToken.PreferredUsername = user.Name
 			idToken.Profile = user.HTMLURL()
 			idToken.Picture = user.AvatarLink(ctx)