fix: display DOI validation errors in deposit form

Author: Mohammed Taha Khan

invenio_rdm_records/assets/semantic-ui/js/invenio_rdm_records/src/deposit/fields/Identifiers/PIDField/components/UnmanagedIdentifierCmp.js

@@ -46,15 +46,19 @@ export class UnmanagedIdentifierCmp extends Component {
     const { localIdentifier } = this.state;
     const { form, fieldPath, helpText, pidPlaceholder, disabled } = this.props;
     const fieldError = getFieldErrors(form, fieldPath);
+    const displayError =
+      fieldError && typeof fieldError === "object" && fieldError.message
+        ? fieldError.message
+        : fieldError;
     return (
       <>
-        <Form.Field width={8} error={fieldError}>
+        <Form.Field width={8} error={displayError}>
           <Form.Input
             onChange={(e, { value }) => this.onChange(value)}
             value={localIdentifier}
             placeholder={pidPlaceholder}
             width={16}
-            error={fieldError}
+            error={displayError}
             disabled={disabled}
           />
         </Form.Field>