Add doc on deployment (#52)

Signed-off-by: Anuraag Agrawal <anuraaga@gmail.com>

Author: anuraaga

docs/deployment.md

@@ -0,0 +1,68 @@
+# Deployment
+
+After building a Connect service, you still need to deploy it to production. This guide covers how to
+use a Python application server to run a service.
+
+## Application Servers
+
+Connect services are standard ASGI or WSGI applications that can be run with an off-the-shelf Python
+application server. Generally, any experience in running a Python application can be applied to running
+Connect as-is.
+
+### HTTP/1.1
+
+Connect only requires HTTP/2 for bidirectional streaming RPCs - the vast majority of services can be run
+using HTTP/1.1 without issue. Two servers have long been in use with HTTP/1.1 and have a proven track
+record. If you are unsure what server to use, it is generally a safe bet to use one of them:
+
+- [gunicorn](http://www.gunicorn.org/) for WSGI applications
+- [uvicorn](https://uvicorn.dev/) for ASGI applications
+
+### HTTP/2
+
+If your service uses bidirectional or otherwise want to use HTTP/2, the above servers will not work.
+HTTP/2 support in the Python ecosystem is still relatively young - servers known to support HTTP/2
+with bidirectional streaming are:
+
+- [granian](https://github.com/emmett-framework/granian)
+- [hypercorn](https://hypercorn.readthedocs.io/en/latest/)
+- [pyvoy](https://github.com/curioswitch/pyvoy)
+
+Connect has an extensive test suite to verify compatibility of connect-python with the Connect protocol.
+Unfortunately, we are only able to reliably pass the suite with pyvoy, with other servers occasionally
+having hung requests or stream ordering issues. pyvoy was built with connect-python in mind but is
+very new and needs more time with real-world applications to verify stability.
+
+Keep the above in mind when picking an HTTP/2 server and let us know how it goes if you give any a try.
+When in doubt, if you do not use bidirectional streaming, we recommend one of the HTTP/1.1 servers.
+
+## CORS
+
+Connect services are standard ASGI and WSGI applications so any CORS middleware can be used to
+enable it.
+
+For example, with an ASGI application using the [asgi-cors](https://pypi.org/project/asgi-cors/)
+middleware:
+
+```python
+from asgi_cors import asgi_cors
+
+from greet.v1.greet_connect import GreetServiceASGIApplication
+from server import Greeter
+
+app = GreetServiceASGIApplication(Greeter())
+
+# app is a standard ASGI application - any middleware works as-is
+app = asgi_cors(
+    app,
+    hosts=["https://acme.com"],
+    # POST is used for all APIs except for idempotent unary RPCs that may support GET
+    methods=["GET", "POST"],
+    headers=[
+        "content-type",
+        "connect-protocol-version",
+        "connect-timeout-ms",
+        "x-user-agent",
+    ],
+)
+```