[Apps SDK] Add error message if relationType is missing (#19006)

Before
<img width="2138" height="1434" alt="image"
src="https://github.com/user-attachments/assets/23aa04ae-9994-4ff9-bac8-9f245e6ca05f"
/>


After
<img width="1029" height="610" alt="image"
src="https://github.com/user-attachments/assets/7af48bc0-678d-4451-8cfb-a5e4028f2c2d"
/>

packages/twenty-server/src/engine/metadata-modules/flat-field-metadata/validators/utils/validate-junction-target-settings.util.ts

@@ -34,6 +34,10 @@ export const validateJunctionTargetSettings = ({
 }: ValidateJunctionTargetSettingsArgs): FlatFieldMetadataValidationError[] => {
   const { universalSettings } = universalFlatFieldMetadata;
 
+  if (!isDefined(universalSettings)) {
+    return [];
+  }
+
   const junctionTargetFieldUniversalIdentifier =
     universalSettings.junctionTargetFieldUniversalIdentifier;
 

packages/twenty-server/src/engine/metadata-modules/flat-field-metadata/validators/utils/validate-morph-or-relation-flat-field-join-column-name.util.ts

@@ -1,4 +1,3 @@
-import { msg } from '@lingui/core/macro';
 import { RelationType } from 'twenty-shared/types';
 import { assertUnreachable, isDefined } from 'twenty-shared/utils';
 
@@ -25,6 +24,15 @@ export const validateMorphOrRelationFlatFieldJoinColumName = ({
 }): FlatFieldMetadataValidationError[] => {
   const errors: FlatFieldMetadataValidationError[] = [];
 
+  if (!isDefined(universalFlatFieldMetadata.universalSettings?.relationType)) {
+    errors.push({
+      code: FieldMetadataExceptionCode.INVALID_FIELD_INPUT,
+      message: `Relation field "${universalFlatFieldMetadata.name}" is missing relationType in universalSettings. Expected MANY_TO_ONE or ONE_TO_MANY.`,
+    });
+
+    return errors;
+  }
+
   switch (universalFlatFieldMetadata.universalSettings.relationType) {
     case RelationType.MANY_TO_ONE: {
       if (
@@ -34,7 +42,6 @@ export const validateMorphOrRelationFlatFieldJoinColumName = ({
           code: FieldMetadataExceptionCode.INVALID_FIELD_INPUT,
           message:
             'Many to one field metadata should carry the join column name in its settings',
-          userFriendlyMessage: msg`A many to one relation field should always declare a join column`,
         });
 
         return errors;
@@ -50,7 +57,6 @@ export const validateMorphOrRelationFlatFieldJoinColumName = ({
         errors.push({
           code: FieldMetadataExceptionCode.INVALID_FIELD_INPUT,
           message: 'Could not find relation field parent flat object',
-          userFriendlyMessage: msg`Could not find relation field parent flat object`,
         });
 
         return errors;
@@ -74,7 +80,6 @@ export const validateMorphOrRelationFlatFieldJoinColumName = ({
           code: FieldMetadataExceptionCode.INVALID_FIELD_INPUT,
           message:
             'One to many field metadata should not carry the join column name in its settings',
-          userFriendlyMessage: msg`A one to many relation field should never declare a join column`,
         });
       }
       break;

packages/twenty-server/src/engine/metadata-modules/flat-field-metadata/validators/utils/validate-morph-or-relation-flat-field-on-delete.util.ts

@@ -14,6 +14,10 @@ export const validateMorphOrRelationFlatFieldOnDelete = ({
 }): FlatFieldMetadataValidationError[] => {
   const errors: FlatFieldMetadataValidationError[] = [];
 
+  if (!isDefined(universalFlatFieldMetadata.universalSettings?.relationType)) {
+    return errors;
+  }
+
   if (
     isDefined(universalFlatFieldMetadata.universalSettings.onDelete) &&
     universalFlatFieldMetadata.universalSettings.relationType !==