[5.1.x] Fixed #36128 -- Clarified auto-generated unique constraint on m2m through models.

Backport of ae2736ca3bf4c6a27e23ee95530ad965b550d4cc from main.

1 files changed, 7 insertions, 0 deletions

diff --git a/docs/ref/contrib/admin/index.txt b/docs/ref/contrib/admin/index.txt
index 4a8b52c18f..39dc4386cb 100644
--- a/docs/ref/contrib/admin/index.txt
+++ b/docs/ref/contrib/admin/index.txt
@@ -2635,6 +2635,13 @@ we can do this with inline admin models. Suppose we have the following models::
         date_joined = models.DateField()
         invite_reason = models.CharField(max_length=64)
 
+        class Meta:
+            constraints = [
+                models.UniqueConstraint(
+                    fields=["person", "group"], name="unique_person_group"
+                )
+            ]
+
 The first step in displaying this intermediate model in the admin is to
 define an inline class for the ``Membership`` model::