web-server: Document reverse proxy configuration

Author: isak-jakobsson

web-server/README.md

@@ -1,12 +1,24 @@
 *Copyright (C) 2021, Axis Communications AB, Lund, Sweden. All Rights Reserved.*
 
-# Serve HTTP requests in an ACAP application
+# Serve HTTP requests through reverse proxy
 
 This example demonstrates how to setup the Axis device web server (Apache) in a
 [Reverse Proxy](https://httpd.apache.org/docs/2.4/howto/reverse_proxy.html)
 configuration, where HTTP requests to the application are routed to a web server
-[Monkey](https://github.com/monkey/monkey) running in the ACAP application and
-acting as a CGI.
+[Monkey](https://github.com/monkey/monkey) running inside the ACAP application
+and acting as a CGI.
+
+The advantage of a webserver proxy is that when porting existing code to your
+ACAP application, its request handling can remain largely unmodified. This eases
+the task of sharing code between platforms. The webserver proxy method enforces
+a URL routing scheme as follows:
+
+`http://<AXIS_DEVICE_IP>/local/<appName>/<apiPath>`
+
+With `<appName>` and `<apiPath>` as defined in the manifest.
+
+Note that this example shows the reverse proxy concept using Monkey, but you are
+free to use any webserver of your choice.
 
 ## Alternative approach
 
@@ -27,6 +39,12 @@ application. In `manifest.json` under `configuration`, it is possible to specify
 a `settingPage` and a `reverseProxy` where the latter will connect the Monkey
 server to the Apache server.
 
+Prior to manifest 1.5.0, reverse proxy was only supported through the
+postinstall script. The manifest based method is more strict on URLs in order to
+avoid name clashes that could occur in the old mechanism. When upgrading, your
+URLs will change to the format shown in
+[Serve HTTP requests through reverse proxy](#serve-http-requests-through-reverse-proxy).
+
 The web server running in the ACAP application can also be exposed directly to
 the network by allowing external access to the port in the network
 configuration for the device. There are disadvantages with exposing Web
@@ -68,7 +86,7 @@ web-server
 
 - Apache Reverse Proxy can not translate content with absolute addresses (i.e.
   /image.png) in the HTML page. Use only relative content (i.e. image.png or
-../image.png)). More information how to handle relative URLs correctly with a
+../image.png). More information how to handle relative URLs correctly with a
 reverse proxy
 [here](https://serverfault.com/questions/561892/how-to-handle-relative-urls-correctly-with-a-reverse-proxy).
 
@@ -145,11 +163,6 @@ As can be seen it's HTML code, browse to web page
 `http://<AXIS_DEVICE_IP>/local/web_server_rev_proxy/my_web_server`
 for seeing it rendered.
 
-> [!NOTE]
->
-> - The API path is `<AXIS_DEVICE_IP>/local/<appName>/<apiPath>` where
->   `appName` and `apiPath` are fields from `manifest.json`.
-
 The application log can be found by either
 
 - Browse to `http://<AXIS_DEVICE_IP>/axis-cgi/admin/systemlog.cgi?appname=web_server_rev_proxy`.