fix: do not fail on missing urls in config

internal/config/config_handler.go

@@ -175,7 +175,8 @@ func parseStringAsURL() mapstructure.DecodeHookFuncType {
 			return nil, fmt.Errorf("cannot cast URL value to string")
 		}
 		if dataStr == "" {
-			return nil, fmt.Errorf("empty values are not allowed for URLs")
+			// NOTE: In some cases a url is optional and in this case the field is just ""
+			return nil, nil
 		}
 		url, err := url.Parse(dataStr)
 		if err != nil {

internal/config/login.go

@@ -59,5 +59,8 @@ func (c LoginConfig) Validate(e RunningEnvironment) error {
 	if c.EnableV1Services && !c.EnableInternalGitlab {
 		return fmt.Errorf("enabling V1 (legacy) services but disabling the internal Gitlab is not supported in the login config")
 	}
+	if c.RenkuBaseURL == nil {
+		return fmt.Errorf("the renkuBaseURL cannot be null or ''")
+	}
 	return nil
 }

internal/config/revproxy.go

@@ -43,6 +43,9 @@ func (r *RevproxyConfig) Validate() error {
 	if r.EnableV1Services && !r.EnableInternalGitlab {
 		return fmt.Errorf("enabling V1 (legacy) services but disabling the internal Gitlab is not supported in the reverse proxy config")
 	}
+	if r.RenkuBaseURL == nil {
+		return fmt.Errorf("the renkuBaseURL cannot be null or ''")
+	}
 
 	// Check v1 services if needed
 	if r.EnableV1Services {