add openapi overriding

docs/references/api/openapi.rst

@@ -43,3 +43,53 @@ You can use a tool like `Swagger UI <https://swagger.io/tools/swagger-ui/>`_ to
 
   The OpenAPI information can go out of date as the schema changes under a running server. To learn how to refresh the cache see :ref:`schema_reloading`.
 
+.. _override_openapi:
+
+Overriding OpenAPI response
+---------------------------
+
+You can override the default response with a function result. To do this, set the function on :ref:`db-root-spec`.
+
+.. code:: bash
+
+   db-root-spec = "root"
+
+.. code:: postgres
+
+  create or replace function root() returns json as $_$
+  declare
+  openapi json = $$
+    {
+      "swagger": "2.0",
+      "info":{
+        "title":"Overridden",
+        "description":"This is a my own API"
+      }
+    }
+  $$;
+  begin
+    return openapi;
+  end
+  $_$ language plpgsql;
+
+.. tabs::
+
+  .. code-tab:: http
+
+    GET / HTTP/1.1
+
+  .. code-tab:: bash Curl
+
+    curl http://localhost:3000
+
+.. code-block:: http
+
+  HTTP/1.1 200 OK
+
+  {
+    "swagger": "2.0",
+    "info":{
+      "title":"Overridden",
+      "description":"This is a my own API"
+    }
+  }

docs/references/configuration.rst

@@ -387,6 +387,18 @@ db-prepared-statements
 
   You should only set this to ``false`` when using PostgresSQL behind an external connection pooler such as PgBouncer working in transaction pooling mode. See :ref:`this section <external_connection_poolers>` for more information.
 
+.. _db-root-spec:
+
+db-root-spec
+------------
+
+  =============== =================
+  **Environment** PGRST_DB_ROOT_SPEC
+  **In-Database** pgrst.db_root_spec
+  =============== =================
+
+  Function to override the OpenAPI response. See :ref:`override_openapi`.
+
 .. _db-schemas:
 
 db-schemas

docs/releases/v11.0.0.rst

@@ -9,6 +9,11 @@ Horizontal Filtering
 
 - New ``isdistinct`` :ref:`operator <operators>`. It is a direct translation of `IS DINTINCT FROM <https://www.postgresql.org/docs/current/functions-comparison.html#FUNCTIONS-COMPARISON-PRED-TABLE>`_.
 
+OpenAPI
+~~~~~~~
+
+- Allow :ref:`override_openapi`.
+
 Admin
 ~~~~~