Add primary_answer field to AnatomyQuestion model and create migration to backfill existing values

anatomy/models.py

@@ -127,6 +127,15 @@ class AnatomyQuestion(QuestionBase):
         related_name="anatomy_authored_questions",
     )
 
+    primary_answer = models.ForeignKey(
+        'Answer',
+        null=True,
+        blank=True,
+        on_delete=models.SET_NULL,
+        related_name='primary_for_questions',
+        help_text="Optional explicit primary answer for this question",
+    )
+
     class Meta:
         permissions = ()
 
@@ -151,33 +160,32 @@ class AnatomyQuestion(QuestionBase):
     def get_absolute_url(self):
         return reverse("anatomy:question_detail", kwargs={"pk": self.pk})
 
-    def get_primary_answer(self):
-        if hasattr(self, "prefetched_primary_answer") and self.prefetched_primary_answer:
-            ans = self.prefetched_primary_answer[0]
-        else:
-            ans = self.answers.filter(
-                proposed=False, status=Answer.MarkOptions.CORRECT
-            ).first()
-        # ans = self.answers.first()
+    def get_primary_answer_obj(self):
+        """Return the Answer instance considered the primary answer, or None.
 
+        Preference order:
+        - explicit `primary_answer` FK if set
+        - `prefetched_primary_answer` if provided by a queryset
+        - first non-proposed Answer with status CORRECT
+        """
+        if getattr(self, "primary_answer", None):
+            return self.primary_answer
+
+        if hasattr(self, "prefetched_primary_answer") and self.prefetched_primary_answer:
+            return self.prefetched_primary_answer[0]
+
+        return self.answers.filter(proposed=False, status=Answer.MarkOptions.CORRECT).first()
+
+    def get_primary_answer(self):
+        """Return the primary answer text (string) for templates and display.
+
+        Keeps backward compatibility by returning the answer string when
+        available, or "None yet..." if no primary answer is defined.
+        """
+        ans = self.get_primary_answer_obj()
         if ans is None:
             return "None yet..."
-        else:
-            return ans.answer
-
-        if (
-            self.answers.filter(
-                proposed=False, status=Answer.MarkOptions.CORRECT
-            ).count()
-            > 0
-        ):
-            return (
-                self.answers.filter(proposed=False, status=Answer.MarkOptions.CORRECT)
-                .first()
-                .answer
-            )
-        else:
-            return "None yet..."
+        return ans.answer
 
     def get_exams(self):
         e = self.exams.all().values_list("name", flat=True)