Add a configurable URL redirect parameter for error URLs

docs/user-guide/nginx-configuration/annotations.md

@@ -440,6 +440,8 @@ Additionally it is possible to set:
   `<Method>` to specify the HTTP method to use.
 * `nginx.ingress.kubernetes.io/auth-signin`:
   `<SignIn_URL>` to specify the location of the error page.
+* `nginx.ingress.kubernetes.io/auth-signin-redirect-param`:
+  `<SignIn_URL>` to specify the URL parameter in the error page which should contain the original URL for a failed signin request.
 * `nginx.ingress.kubernetes.io/auth-response-headers`:
   `<Response_Header_1, ..., Response_Header_n>` to specify headers to pass to backend once authentication request completes.
 * `nginx.ingress.kubernetes.io/auth-proxy-set-headers`:

docs/user-guide/nginx-configuration/configmap.md

@@ -176,6 +176,7 @@ The following table shows a configuration option's name, type, and the default v
 |[global-auth-url](#global-auth-url)|string|""|
 |[global-auth-method](#global-auth-method)|string|""|
 |[global-auth-signin](#global-auth-signin)|string|""|
+|[global-auth-signin-redirect-param](#global-auth-signin-redirect-param)|string|"rd"|
 |[global-auth-response-headers](#global-auth-response-headers)|string|""|
 |[global-auth-request-redirect](#global-auth-request-redirect)|string|""|
 |[global-auth-snippet](#global-auth-snippet)|string|""|
@@ -1048,6 +1049,12 @@ Sets the location of the error page for an existing service that provides authen
 Similar to the Ingress rule annotation `nginx.ingress.kubernetes.io/auth-signin`.
 _**default:**_ ""
 
+## global-auth-signin-redirect-param
+
+Sets the query parameter in the error page signin URL which contains the original URL of the request that failed authentication.
+Similar to the Ingress rule annotation `nginx.ingress.kubernetes.io/auth-signin-redirect-param`.
+_**default:**_ "rd"
+
 ## global-auth-response-headers
 
 Sets the headers to pass to backend once authentication request completes. Applied to all the locations.