Allow unknown for is operator

api.rst

@@ -72,7 +72,7 @@ ilike         :code:`ILIKE`             ILIKE operator (use * in place of %)
 in            :code:`IN`                one of a list of values, e.g. :code:`?a=in.(1,2,3)`
                                         – also supports commas in quoted strings like
                                         :code:`?a=in.("hi,there","yes,you")`
-is            :code:`IS`                checking for exact equality (null,true,false)
+is            :code:`IS`                checking for exact equality (null,true,false,unknown)
 fts           :code:`@@`                :ref:`fts` using to_tsquery
 plfts         :code:`@@`                :ref:`fts` using plainto_tsquery
 phfts         :code:`@@`                :ref:`fts` using phraseto_tsquery

releases/upcoming.rst

@@ -38,6 +38,9 @@ Added
 * Allow calling a function with a :ref:`single unnamed parameter <s_proc_single_unnamed>` to POST raw ``json/jsonb``, ``bytea`` or ``text``.
   |br| -- `@steve-chavez <https://github.com/steve-chavez>`_
 
+* Allow specifying ``unknown`` for the ``is`` :ref:`operator <operators>`.
+  |br| -- `@steve-chavez <https://github.com/steve-chavez>`_
+
 * Documentation improvements
 
   + Added :ref:`nested_embedding` to the :ref:`resource_embedding` section.