Fixed #32466 -- Corrected autocomplete to_field resolution for complex cases.

In MTI or ForeignKey as primary key cases, it is required to fetch the attname
from the field instance on the remote model in order to reliably resolve the
to_field_name.

Co-authored-by: Johannes Maron <info@johanneshoppe.com>
Co-authored-by: Mariusz Felisiak <felisiak.mariusz@gmail.com>
Co-authored-by: Carlton Gibson <carlton.gibson@noumenal.es>

tests/admin_widgets/models.py

@@ -18,7 +18,11 @@ class Member(models.Model):
         return self.name
 
 
-class Band(models.Model):
+class Artist(models.Model):
+    pass
+
+
+class Band(Artist):
     uuid = models.UUIDField(unique=True, default=uuid.uuid4)
     name = models.CharField(max_length=100)
     style = models.CharField(max_length=20)
@@ -47,6 +51,25 @@ class Album(models.Model):
         return self.name
 
 
+class ReleaseEvent(models.Model):
+    """
+    Used to check that autocomplete widget correctly resolves attname for FK as
+    PK example.
+    """
+    album = models.ForeignKey(Album, models.CASCADE, primary_key=True)
+    name = models.CharField(max_length=100)
+
+    class Meta:
+        ordering = ['name']
+
+    def __str__(self):
+        return self.name
+
+
+class VideoStream(models.Model):
+    release_event = models.ForeignKey(ReleaseEvent, models.CASCADE)
+
+
 class HiddenInventoryManager(models.Manager):
     def get_queryset(self):
         return super().get_queryset().filter(hidden=False)