Generalized check constraint docs for other constraints.

docs/ref/models/constraints.txt

@@ -1,6 +1,6 @@
-===========================
-Check constraints reference
-===========================
+=====================
+Constraints reference
+=====================
 
 .. module:: django.db.models.constraints
 
@@ -8,20 +8,19 @@ Check constraints reference
 
 .. versionadded:: 2.2
 
-The ``CheckConstraint`` class creates database check constraints. They are
-added in the model :attr:`Meta.constraints
-<django.db.models.Options.constraints>` option. This document
-explains the API references of :class:`CheckConstraint`.
+The classes defined in this module create database constraints. They are added
+in the model :attr:`Meta.constraints <django.db.models.Options.constraints>`
+option.
 
 .. admonition:: Referencing built-in constraints
 
     Constraints are defined in ``django.db.models.constraints``, but for
     convenience they're imported into :mod:`django.db.models`. The standard
     convention is to use ``from django.db import models`` and refer to the
-    constraints as ``models.CheckConstraint``.
+    constraints as ``models.<Foo>Constraint``.
 
-``CheckConstraint`` options
-===========================
+``CheckConstraint``
+===================
 
 .. class:: CheckConstraint(*, check, name)
 

docs/ref/models/index.txt

@@ -9,7 +9,7 @@ Model API reference. For introductory material, see :doc:`/topics/db/models`.
 
    fields
    indexes
-   check-constraints
+   constraints
    meta
    relations
    class

docs/ref/models/options.txt

@@ -459,8 +459,8 @@ Django quotes column and table names behind the scenes.
 
     .. versionadded:: 2.2
 
-    A list of :doc:`constraints </ref/models/check-constraints>` that you want
-    to define on the model::
+    A list of :doc:`constraints </ref/models/constraints>` that you want to
+    define on the model::
 
         from django.db import models
 

docs/releases/2.2.txt

@@ -30,8 +30,8 @@ officially support the latest release of each series.
 What's new in Django 2.2
 ========================
 
-Check Constraints
------------------
+Constraints
+-----------
 
 The new :class:`~django.db.models.CheckConstraint` class enables adding custom
 database constraints. Constraints are added to models using the