Refactor NormalCase model: remove 'added_by' field, add 'author' ManyToManyField; update related views and templates for editing functionality

atlas/models.py

@@ -766,7 +766,7 @@ class Case(models.Model, AuthorMixin, QuestionMixin):
         return json.dumps(results)
 
 
-class NormalCase(models.Model):
+class NormalCase(models.Model, AuthorMixin):
     """Marks a Case as a 'normal' example used in the Atlas normals section.
 
     This version stores a canonical `age_days` integer (patient age in days).
@@ -819,16 +819,15 @@ class NormalCase(models.Model):
         help_text="Primary modality for this normal case (optional).",
     )
 
-    added_by = models.ForeignKey(
-        settings.AUTH_USER_MODEL,
-        null=True,
-        blank=True,
-        on_delete=models.SET_NULL,
-        related_name="added_normals",
-    )
-
     added_date = models.DateTimeField(default=timezone.now)
 
+
+    author = models.ManyToManyField(
+        settings.AUTH_USER_MODEL,
+        blank=True,
+        related_name="normal_cases",
+    )
+
     notes = models.TextField(null=True, blank=True)
 
     class Meta: