Disable local users for a smooth single-idp mode (#5226)

Add LocalAuthDisabled option to embedded IdP configuration

This adds the ability to disable local (email/password) authentication when using the embedded Dex identity provider. When disabled, users can only authenticate via external
identity providers (Google, OIDC, etc.).

This simplifies user login when there is only one external IdP configured. The login page will redirect directly to the IdP login page.

Key changes:

Added LocalAuthDisabled field to EmbeddedIdPConfig
Added methods to check and toggle local auth: IsLocalAuthEnabled, HasNonLocalConnectors, DisableLocalAuth, EnableLocalAuth
Validation prevents disabling local auth if no external connectors are configured
Existing local users are preserved when disabled and can login again when re-enabled
Operations are idempotent (disabling already disabled is a no-op)

idp/dex/connector.go

@@ -327,6 +327,60 @@ func ensureLocalConnector(ctx context.Context, stor storage.Storage) error {
 	return nil
 }
 
+// HasNonLocalConnectors checks if there are any connectors other than the local connector.
+func (p *Provider) HasNonLocalConnectors(ctx context.Context) (bool, error) {
+	connectors, err := p.storage.ListConnectors(ctx)
+	if err != nil {
+		return false, fmt.Errorf("failed to list connectors: %w", err)
+	}
+
+	p.logger.Info("checking for non-local connectors", "total_connectors", len(connectors))
+	for _, conn := range connectors {
+		p.logger.Info("found connector in storage", "id", conn.ID, "type", conn.Type, "name", conn.Name)
+		if conn.ID != "local" || conn.Type != "local" {
+			p.logger.Info("found non-local connector", "id", conn.ID)
+			return true, nil
+		}
+	}
+	p.logger.Info("no non-local connectors found")
+	return false, nil
+}
+
+// DisableLocalAuth removes the local (password) connector.
+// Returns an error if no other connectors are configured.
+func (p *Provider) DisableLocalAuth(ctx context.Context) error {
+	hasOthers, err := p.HasNonLocalConnectors(ctx)
+	if err != nil {
+		return err
+	}
+	if !hasOthers {
+		return fmt.Errorf("cannot disable local authentication: no other identity providers configured")
+	}
+
+	// Check if local connector exists
+	_, err = p.storage.GetConnector(ctx, "local")
+	if errors.Is(err, storage.ErrNotFound) {
+		// Already disabled
+		return nil
+	}
+	if err != nil {
+		return fmt.Errorf("failed to check local connector: %w", err)
+	}
+
+	// Delete the local connector
+	if err := p.storage.DeleteConnector(ctx, "local"); err != nil {
+		return fmt.Errorf("failed to delete local connector: %w", err)
+	}
+
+	p.logger.Info("local authentication disabled")
+	return nil
+}
+
+// EnableLocalAuth creates the local (password) connector if it doesn't exist.
+func (p *Provider) EnableLocalAuth(ctx context.Context) error {
+	return ensureLocalConnector(ctx, p.storage)
+}
+
 // ensureStaticConnectors creates or updates static connectors in storage
 func ensureStaticConnectors(ctx context.Context, stor storage.Storage, connectors []Connector) error {
 	for _, conn := range connectors {