Add sub-app to generate open api spec

aiohttp_pydantic/oas/__init__.py

@@ -0,0 +1,26 @@
+from typing import Iterable
+from importlib import resources
+
+import jinja2
+from aiohttp import web
+from .view import get_oas, oas_ui
+from swagger_ui_bundle import swagger_ui_path
+
+
+def setup(
+    app: web.Application,
+    apps_to_expose: Iterable[web.Application] = (),
+    url_prefix: str = "/oas",
+    enable: bool = True,
+):
+    if enable:
+        oas_app = web.Application()
+        oas_app["apps to expose"] = tuple(apps_to_expose) or (app,)
+        oas_app["index template"] = jinja2.Template(
+            resources.read_text("aiohttp_pydantic.oas", "index.j2")
+        )
+        oas_app.router.add_get("/spec", get_oas, name="spec")
+        oas_app.router.add_static("/static", swagger_ui_path, name="static")
+        oas_app.router.add_get("", oas_ui, name="index")
+
+        app.add_subapp(url_prefix, oas_app)