udpate instrcutions on aiohttp

Author: pcrespov

.github/instructions/python.instructions.md

@@ -35,6 +35,8 @@ Ensure compatibility with the following library versions:
 
 * Use `f-string` formatting for all string interpolation except for logging message strings.
 * Use **relative imports** within the same package/module.
+  - For imports within the same repository/project, always use relative imports (e.g., `from ..constants import APP_SETTINGS_KEY` instead of `from simcore_service_webserver.constants import APP_SETTINGS_KEY`)
+  - Use absolute imports only for external libraries and packages
 * Place **all imports at the top** of the file.
 * Document functions when the code is not self-explanatory or if asked explicitly.
 
@@ -44,6 +46,18 @@ Ensure compatibility with the following library versions:
 * Prefer `json_dumps` / `json_loads` from `common_library.json_serialization` instead of the built-in `json.dumps` / `json.loads`.
 * When using Pydantic models, prefer methods like `model.model_dump_json()` for serialization.
 
-### 7. **Running tests**
+### 7. **aiohttp Framework**
+
+* **Application Keys**: Always use `web.AppKey` for type-safe application storage instead of string keys
+  - Define keys with specific types: `APP_MY_KEY: Final = web.AppKey("APP_MY_KEY", MySpecificType)`
+  - Use precise types instead of generic `object` when the actual type is known
+  - Example: `APP_SETTINGS_KEY: Final = web.AppKey("APP_SETTINGS_KEY", ApplicationSettings)`
+  - Store and retrieve: `app[APP_MY_KEY] = value` and `data = app[APP_MY_KEY]`
+* **Request Keys**: Use `web.AppKey` for request storage as well for consistency and type safety
+* **Middleware**: Follow the repository's middleware patterns for cross-cutting concerns
+* **Error Handling**: Use the established exception handling decorators and patterns
+* **Route Definitions**: Use `web.RouteTableDef()` and organize routes logically within modules
+
+### 8. **Running tests**
 * Use `--keep-docker-up` flag when testing to keep docker containers up between sessions.
 * Always activate the python virtual environment before running pytest.