docs: add docs for proxy provider

docs/build.sh

@@ -1,3 +0,0 @@
-#!/bin/bash -x
-pip install -U mkdocs mkdocs-material
-mkdocs gh-deploy

docs/providers/proxy.md

@@ -0,0 +1,13 @@
+# Proxy Provider
+
+This provider protects applications, which have no built-in support for OAuth2 or SAML. This is done by running a lightweight Reverse Proxy in front of the application, which authenticates the requests.
+
+passbook Proxy is based on [oauth2_proxy](https://github.com/oauth2-proxy/oauth2-proxy), but has been integrated more tightly with passbook.
+
+The Proxy these extra headers to the application:
+
+Header Name | Value
+-------------|-------
+X-Auth-Request-User | The user's unique identifier
+X-Auth-Request-Email | The user's email address
+X-Auth-Request-Preferred-Username | The user's username

docs/upgrading/to-0.10.md

@@ -10,6 +10,8 @@ This update brings a lot of big features, such as:
 
   Due to this new OAuth2 Provider, the Application Gateway Provider, now simply called "Proxy Provider" has been revamped as well. The new passbook Proxy integrates more tightly with passbook via the new Outposts system. The new proxy also supports multiple applications per proxy instance, can configure TLS based on passbook Keypairs and more.
 
+  See [Proxy](../providers/proxy.md)
+
 - Outpost System
 
   This is a new Object type, used currently only by the Proxy Provider. It manages the creation and permissions of service accounts, which are used by the outposts to communicate with passbook.

mkdocs.yml

@@ -29,6 +29,7 @@ nav:
   - Providers:
     - OAuth2: providers/oauth2.md
     - SAML: providers/saml.md
+    - Proxy: providers/proxy.md
   - Expressions:
     - Overview: expressions/index.md
     - Reference: