Adding specific UI error code for duplicate group name.

Author: krulis-martin

app/V1Module/presenters/GroupsPresenter.php

@@ -1374,7 +1374,8 @@ private function updateLocalizations(Request $req, Group $group): void
                     if ($otherGroup !== $group) {
                         throw new InvalidApiArgumentException(
                             'name',
-                            "There is already a group of this name, please choose a different one."
+                            "There is already a group of this name, please choose a different one.",
+                            FrontendErrorMappings::E400_504__GROUP_DUPLICATE_NAME
                         );
                     }
                 }

app/exceptions/FrontendErrorMappings.php

@@ -65,6 +65,8 @@ class FrontendErrorMappings
     public const E400_502__GROUP_INSTANCE_ROOT_CANNOT_RELOCATE = "400-502";
     /** Relocation of a group would create a loop in the tree hierarchy (new parent is a child of a group or group itself). */
     public const E400_503__GROUP_RELOCATION_WOULD_CREATE_LOOP = "400-503";
+    /** Group cannot be created/renamed because another group with the same name already exists in the parent group */
+    public const E400_504__GROUP_DUPLICATE_NAME = "400-504";
 
     /** General unauthorized */
     public const E401_000__UNAUTHORIZED = "401-000";