Auth: Fix AzureAD public client configuration (#99019)

Auth: Add client auth none as default to ensure public clients can be configured on the UI

pkg/login/social/connectors/azuread_oauth.go

@@ -199,7 +199,7 @@ func (s *SocialAzureAD) Exchange(ctx context.Context, code string, authOptions .
 	case social.ClientSecretPost:
 		// Default behavior for ClientSecretPost, no additional setup needed
 	default:
-		s.log.Debug("ClientAuthentication is not set. Using default client authentication method")
+		s.log.Debug("ClientAuthentication is not set. Using default client authentication method: none")
 	}
 
 	// Default token exchange
@@ -379,6 +379,9 @@ func validateClientAuthentication(info *social.OAuthInfo, requester identity.Req
 		}
 		return nil
 
+	case social.None:
+		return nil
+
 	default:
 		return ssosettings.ErrInvalidOAuthConfig("Invalid client authentication method.")
 	}

pkg/login/social/social.go

@@ -16,6 +16,7 @@ const (
 
 	// Values for ClientAuthentication under OAuthInfo (based on oidc spec)
 	ClientSecretPost = "client_secret_post"
+	None             = "none"
 	// Azure AD
 	ManagedIdentity = "managed_identity"
 	// Other providers...