Allow to pass a str to the Python aiohttp client (#18985)

* see #18972

Add support for `str`

* update python samples

---------

Co-authored-by: David Riccitelli <[email protected]>

Author: wing328

modules/openapi-generator/src/main/resources/python/asyncio/rest.mustache

@@ -177,10 +177,10 @@ class RESTClientObject:
                         data.add_field(k, v)
                 args["data"] = data
 
-            # Pass a `bytes` parameter directly in the body to support
+            # Pass a `bytes` or `str` parameter directly in the body to support
             # other content types than Json when `body` argument is provided
             # in serialized form
-            elif isinstance(body, bytes):
+            elif isinstance(body, str) or isinstance(body, bytes):
                 args["data"] = body
             else:
                 # Cannot generate the request from given parameters

samples/openapi3/client/petstore/python-aiohttp/petstore_api/rest.py

@@ -187,10 +187,10 @@ async def request(
                         data.add_field(k, v)
                 args["data"] = data
 
-            # Pass a `bytes` parameter directly in the body to support
+            # Pass a `bytes` or `str` parameter directly in the body to support
             # other content types than Json when `body` argument is provided
             # in serialized form
-            elif isinstance(body, bytes):
+            elif isinstance(body, str) or isinstance(body, bytes):
                 args["data"] = body
             else:
                 # Cannot generate the request from given parameters