LIBDRUM-909. Force re-display of validation errors

These changes are an attempt to fix an apparent race condition between
the Angular field validation and the DSpace refresh of the page on
attempted submission.

The issue being fixed is that the GUI validation error warnings
momentarily "flash" and then disappear when submitting the form using
the "Deposit" button.

The workflow appears to be:

* The user does not focus on or enter anything in a required field, and
  then attempts to submit the form.
* The request to the DSpace backend does not include any JSON related to
  the required field
* A 200 response is returned from the DSpace backend, with an "errors"
  array in the JSON, indicating the validation error
* The 200 response triggers a page refresh, which wipes out any existing
  validation error display on the page.

This change forces all the validation errors to be re-displayed by
touching the relevant fields and triggering a validity check after the
page is refreshed.

It is unclear whether this is the optimal fix, so it has not been
submitted upstream to DSpace. Also, DSpace has been working on various
fixes, so the changes in this class should be re-evaluated on upgrades,
and removed if possible.

https://umd-dit.atlassian.net/browse/LIBDRUM-909

Author: dsteelma-umd

src/app/submission/sections/form/section-form.component.ts

@@ -395,7 +395,14 @@ export class SubmissionSectionFormComponent extends SectionModelComponent {
       .subscribe(() => {
         this.sectionService.checkSectionErrors(this.submissionId, this.sectionData.id, this.formId, errors, this.sectionData.errorsToShow);
         this.sectionData.errorsToShow = errors;
+
+        // UMD Customization
+        // Ensure that any validation errors are marked
+        if (isNotEmpty(errors) && this.formRef?.formGroup) {
+          this.formService.validateAllFormFields(this.formRef.formGroup);
+        }
         this.cdr.detectChanges();
+        // End UMD Customzation
       });
   }