Document FastAPI endpoint example (#8)

Signed-off-by: Federico Busetti <[email protected]>

Author: febus982

docs/protocol_bindings/http_binding.md

@@ -129,6 +129,49 @@ print(type(http_handler.from_json(customer_event_json)))
 ```
 ///
 
+### FastAPI
+
+Both this package and [FastAPI](https://fastapi.tiangolo.com/) are built on top
+of [Pydantic](https://docs.pydantic.dev/latest/). This means you don't need to instantiate
+a `HTTPHandler` to receive CloudEvents using a [FastAPI](https://fastapi.tiangolo.com/) endpoint.
+
+```python
+### Event classes omitted ###
+
+Event = Annotated[
+    Union[OrderCreatedEvent, CustomerCreatedEvent],
+    Field(discriminator="type"),
+]
+
+# Endpoint for single events
+@router.post("/event", status_code=204)
+async def submit_event(
+    event: Annotated[Event, Body()],
+    content_type: Annotated[
+        Literal["application/cloudevents+json; charset=UTF-8"], Header()
+    ],
+) -> None:
+    do_something(event)
+
+# Endpoint for event batches
+@router.post("/batch", status_code=204)
+async def submit_event_batch(
+    event_batch: Annotated[List[Event], Body()],
+    content_type: Annotated[
+        Literal["application/cloudevents-batch+json; charset=UTF-8"], Header()
+    ],
+) -> None:
+    for event in event_batch:
+        do_something(event)
+```
+
+/// admonition | Generate the OpenAPI schema correctly
+    type: tip
+
+In order to have the OpenAPI spec correctly generated by FastAPI you'll need to
+work around some FastAPI limitations and manually specify some of the needed data.
+You can find a detailed example [here](https://github.com/febus982/bootstrap-python-fastapi/blob/main/src/http_app/routes/events.py).
+///
 
 ## Serialize a JSON event