config: add rewrite_response_headers option (#1961)

* add lua script to rewrite response headers

* add policy config

* update docs

docs/reference/readme.md

@@ -1294,6 +1294,30 @@ Remove Request Headers allows you to remove given request headers. This can be u
 ```
 
 
+### Rewrite Response Headers
+- Config File Key: `rewrite_response_headers`
+- Type: `object`
+- Optional
+- Example: `[{ "header": "Location", "prefix": "http://localhost:8000/two/", "value": "http://frontend/one/" }]`
+
+Rewrite Response Headers allows you to modify response headers before they are returned to the client. The `header` field will match the HTTP header name, and `prefix` will be replaced with `value`. For example, if the downstream server returns a header:
+
+```text
+Location: http://localhost:8000/two/some/path/
+```
+
+And the policy has this config:
+
+```yaml
+rewrite_response_headers:
+  - header: Location
+    prefix: http://localhost:8000/two/
+    value: http://frontend/one/
+```
+
+The browser would be redirected to: `http://frontend/one/some/path/`. This is similar to nginx's [`proxy_redirect` option](http://nginx.org/en/docs/http/ngx_http_proxy_module.html#proxy_redirect), but can be used for any header.
+
+
 ### Redirect
 - `yaml`/`json` setting: 'redirect'
 - Type: object

docs/reference/settings.yaml

@@ -1427,6 +1427,30 @@ settings:
               - X-Email
               - X-Username
           ```
+      - name: "Rewrite Response Headers"
+        keys: ["rewrite_response_headers"]
+        attributes: |
+          - Config File Key: `rewrite_response_headers`
+          - Type: `object`
+          - Optional
+          - Example: `[{ "header": "Location", "prefix": "http://localhost:8000/two/", "value": "http://frontend/one/" }]`
+        doc: |
+          Rewrite Response Headers allows you to modify response headers before they are returned to the client. The `header` field will match the HTTP header name, and `prefix` will be replaced with `value`. For example, if the downstream server returns a header:
+
+          ```text
+          Location: http://localhost:8000/two/some/path/
+          ```
+
+          And the policy has this config:
+
+          ```yaml
+          rewrite_response_headers:
+            - header: Location
+              prefix: http://localhost:8000/two/
+              value: http://frontend/one/
+          ```
+
+          The browser would be redirected to: `http://frontend/one/some/path/`. This is similar to nginx's [`proxy_redirect` option](http://nginx.org/en/docs/http/ngx_http_proxy_module.html#proxy_redirect), but can be used for any header.
       - name: "Redirect"
         keys: ["redirect"]
         attributes: |