fix: respond with useful information when cert is requsted

 This change simply makes the lms respond with useful data/status
 when learner request for generating a certficate is met.

  This might not have been an issue before (by before we refer to
  the time when the learning expirence wasn't handled by the MFE
  but through Django template base/server side rendering) however
  currnelly (to my observation) this view is being only requested
  as a RESTful by the MFE, thus this change transform it a
  RESTful type of view.

  This change goes hand in hand with the learning MFE:
   - openedx/frontend-app-learning/pull/1348

lms/djangoapps/courseware/views/views.py

@@ -66,6 +66,7 @@
 from lms.djangoapps.commerce.utils import EcommerceService
 from lms.djangoapps.course_goals.models import UserActivity
 from lms.djangoapps.course_home_api.toggles import course_home_mfe_progress_tab_is_active
+from lms.djangoapps.course_home_api.progress.serializers import CertificateDataSerializer
 from lms.djangoapps.courseware.access import has_access, has_ccx_coach_role
 from lms.djangoapps.courseware.access_utils import check_public_access
 from lms.djangoapps.courseware.courses import (
@@ -1422,6 +1423,9 @@ def generate_user_cert(request, course_id):
         return HttpResponseBadRequest(_("Course is not valid"))
 
     log.info(f'Attempt will be made to generate a course certificate for {student.id} : {course_key}.')
+    # We get the certificate status before request to create it, this needed
+    # because it could the case that certificate is being quickly generated
+    certificate_status_before = certs_api.certificate_downloadable_status(student, course.id)
 
     try:
         certs_api.generate_certificate_task(student, course_key, 'self')
@@ -1446,13 +1450,27 @@ def generate_user_cert(request, course_id):
         certificate_status["is_downloadable"],
         certificate_status["is_generating"],
     )
-
-    if certificate_status["is_downloadable"]:
-        return HttpResponseBadRequest(_("Certificate has already been created."))
+
+    # By default we assume certficate is generated quickly
+    status_message = _("Your cretficate has been just generated!.")
+    status_code = 200
+
+    if certificate_status["is_downloadable"] and certificate_status_before["is_downloadable"]:
+        status_message = _("Certificate has already been created.")
+        status_code = 400
     elif certificate_status["is_generating"]:
-        return HttpResponseBadRequest(_("Certificate is being created."))
-
-    return HttpResponse()
+        status_message = _("Certificate is being created.")
+        # Todo:
+        # Shall we keep responding with 400? even if request is taken into account...
+        status_code = 400
+
+    if status_code == 400:
+        return JsonResponse({'status_message': status_message },status = status_code)
+    # Now that we are sure we get the cert data in same data structual as if it's progress
+    # page or course outline, hence `CertificateDataSerializer` is used for both
+    # course home view (which which the  data strucucal that the learning MFE expecsts).
+    course_mode = certs_api.certificate_status_for_student(student,course.id).get('mode')
+    return JsonResponse({'certificate_data': CertificateDataSerializer(get_cert_data(student,course,course_mode)).data}, status = status_code)
 
 
 def enclosing_sequence_for_gating_checks(block):