[ENG-8193] Fix issues with Preprint submission via API (#11185)

## Purpose
handle django core ValidationError in drf view

## Ticket
https://openscience.atlassian.net/browse/ENG-8193

Author: antkryt

api/actions/views.py

@@ -1,7 +1,8 @@
+from django.core.exceptions import ValidationError as DjangoValidationError
 from guardian.shortcuts import get_objects_for_user
 from rest_framework import generics
 from rest_framework import permissions
-from rest_framework.exceptions import NotFound, PermissionDenied
+from rest_framework.exceptions import NotFound, PermissionDenied, ValidationError
 
 from api.actions.permissions import ReviewActionPermission
 from api.actions.serializers import NodeRequestActionSerializer, ReviewActionSerializer, PreprintRequestActionSerializer
@@ -186,7 +187,10 @@ def perform_create(self, serializer):
                 ),
             )
 
-        serializer.save(user=self.request.user)
+        try:
+            serializer.save(user=self.request.user)
+        except (ValueError, DjangoValidationError) as exc:
+            raise ValidationError(str(exc)) from exc
 
     # overrides ListFilterMixin
     def get_default_queryset(self):

api_tests/actions/views/test_action_list.py

@@ -366,3 +366,38 @@ def test_invalid_target_id(self, app, moderator):
             expect_errors=True
         )
         assert res.status_code == 404
+
+    def test_submit_preprint_without_files_returns_400(self, app, url, preprint, node_admin):
+        # Ensure preprint has no files
+        preprint.primary_file = None
+        preprint.save()
+
+        submit_payload = self.create_payload(
+            preprint._id,
+            trigger='submit'
+        )
+
+        res = app.post_json_api(
+            url,
+            submit_payload,
+            auth=node_admin.auth,
+            expect_errors=True
+        )
+        assert res.status_code == 400
+
+    def test_provider_not_reviewed_returns_409(self, app, url, preprint, node_admin):
+        preprint.provider = PreprintProviderFactory(reviews_workflow=None)
+        preprint.save()
+
+        submit_payload = self.create_payload(
+            preprint._id,
+            trigger='submit'
+        )
+
+        res = app.post_json_api(
+            url,
+            submit_payload,
+            auth=node_admin.auth,
+            expect_errors=True
+        )
+        assert res.status_code == 409