Fixed #18468 -- Added support for comments on columns and tables.

Thanks Jared Chung, Tom Carrick, David Smith, Nick Pope, and Mariusz
Felisiak for reviews.

Co-authored-by: Mariusz Felisiak <felisiak.mariusz@gmail.com>
Co-authored-by: Nick Pope <nick@nickpope.me.uk>

docs/ref/models/fields.txt

@@ -325,6 +325,21 @@ characters that aren't allowed in Python variable names -- notably, the
 hyphen -- that's OK. Django quotes column and table names behind the
 scenes.
 
+``db_comment``
+--------------
+
+.. versionadded:: 4.2
+
+.. attribute:: Field.db_comment
+
+The comment on the database column to use for this field. It is useful for
+documenting fields for individuals with direct database access who may not be
+looking at your Django code. For example::
+
+    pub_date = models.DateTimeField(
+        db_comment="Date and time when the article was published",
+    )
+
 ``db_index``
 ------------
 

docs/ref/models/options.txt

@@ -91,6 +91,24 @@ Django quotes column and table names behind the scenes.
    backends; except for Oracle, however, the quotes have no effect. See the
    :ref:`Oracle notes <oracle-notes>` for more details.
 
+``db_table_comment``
+--------------------
+
+.. versionadded:: 4.2
+
+.. attribute:: Options.db_table_comment
+
+The comment on the database table to use for this model. It is useful for
+documenting database tables for individuals with direct database access who may
+not be looking at your Django code. For example::
+
+    class Answer(models.Model):
+        question = models.ForeignKey(Question, on_delete=models.CASCADE)
+        answer = models.TextField()
+
+        class Meta:
+            db_table_comment = "Question answers"
+
 ``db_tablespace``
 -----------------