website/docs: add proxy custom header docs

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

website/docs/providers/proxy/custom_headers.md

@@ -0,0 +1,41 @@
+---
+title: Custom headers
+---
+
+The proxy can send custom headers to your upstream application. These can be configured in one of two ways:
+
+- Group attributes; this allows for inheritance, but only allows static values
+- Property mappings; this allows for dynamic values
+
+## Group attributes
+
+Edit the group or user you wish the header to be set for, and set these attributes:
+
+```yaml
+additionalHeaders:
+    X-My-Header: value
+```
+
+You can the add users to this group or override the field in users.
+
+## Property Mappings
+
+For dynamic Header values (for example, your application requires X-App-User to contain the username), property mappings can be used.
+
+Create a new Scope mapping with a name and scope of your choice, and use an expression like this:
+
+```python
+return {
+    "ak_proxy": {
+        "user_attributes": {
+            "additionalHeaders": {
+                "X-App-User": request.user.username
+            }
+        }
+    }
+}
+```
+
+After you've created this Scope mapping, make sure to edit the proxy provider and select the mapping.
+
+As you can see by the similar structure, this just overrides any static attributes, so both of these methods can be combined.

website/docusaurus.config.js

@@ -18,7 +18,7 @@ module.exports = {
                 {
                     to: "docs/",
                     activeBasePath: "docs",
-                    label: "Docs",
+                    label: "Documentation",
                     position: "left",
                 },
                 {
@@ -30,7 +30,7 @@ module.exports = {
                 {
                     to: "developer-docs/",
                     activeBasePath: "developer-docs",
-                    label: "Developer Docs",
+                    label: "Developer",
                     position: "left",
                 },
                 {

website/sidebars.js

@@ -37,6 +37,7 @@ module.exports = {
                     label: "Proxy Provider",
                     items: [
                         "providers/proxy/proxy",
+                        "providers/proxy/custom_headers",
                         "providers/proxy/forward_auth",
                     ],
                 },