chore(): minor fixes around codebase

src/backend/apps/experiments/services.py

@@ -339,6 +339,7 @@ def experiment_submit_for_review(
 def experiment_approve(
     *, experiment: Experiment, approver: User, comment: str = ""
 ) -> Experiment:
+    experiment = Experiment.objects.select_for_update().get(pk=experiment.pk)
     if experiment.status != ExperimentStatus.IN_REVIEW:
         raise ValidationError(
             {"status": "Experiment must be in 'in_review' status to approve."}
@@ -386,6 +387,15 @@ def experiment_approve(
 def experiment_reject(
     *, experiment: Experiment, user: User, comment: str = ""
 ) -> Experiment:
+    if not can_user_approve_experimenter(user, experiment.owner):
+        raise ValidationError(
+            {
+                "user": (
+                    f"User '{user.username}' is not authorized to "
+                    f"reject experiments for '{experiment.owner.username}'."
+                )
+            }
+        )
     experiment = _transition(
         experiment,
         ExperimentStatus.REJECTED,
@@ -401,6 +411,15 @@ def experiment_reject(
 def experiment_request_changes(
     *, experiment: Experiment, user: User, comment: str = ""
 ) -> Experiment:
+    if not can_user_approve_experimenter(user, experiment.owner):
+        raise ValidationError(
+            {
+                "user": (
+                    f"User '{user.username}' is not authorized to "
+                    f"request changes for '{experiment.owner.username}'."
+                )
+            }
+        )
     experiment.approvals.all().delete()
     return _transition(
         experiment,