PR comment followups (isNonEmptyString and rename WorkflowExecutionResult) (#13706)

Addressing two comments from Thomas and Charles

packages/twenty-server/src/engine/core-modules/twenty-config/decorators/is-optional-or-empty-string.decorator.ts

@@ -1,7 +1,8 @@
+import { isNonEmptyString } from '@sniptt/guards';
 import { ValidateIf, ValidationOptions, isDefined } from 'class-validator';
 
 export function IsOptionalOrEmptyString(validationOptions?: ValidationOptions) {
   return ValidateIf((_obj, value) => {
-    return isDefined(value) && value !== '';
+    return isDefined(value) && isNonEmptyString(value);
   }, validationOptions);
 }