Add flags to define CSRF cookie expiration time and to allow CSRF cookies per request (#1708)

* Add start of state to CSRF cookie name

* Update CHANGELOG.md

* Update CHANGELOG.md

* Support optional flags

* Update CHANGELOG.md

* Update CHANGELOG.md

* Update CHANGELOG.md

* Update overview.md

Add new CSRF flags

* Update overview.md

Describe new CSRF flags

Co-authored-by: Nuno Borges <Nuno.Borges@ctw.bmwgroup.com>

docs/docs/configuration/overview.md

@@ -95,6 +95,8 @@ An example [oauth2-proxy.cfg](https://github.com/oauth2-proxy/oauth2-proxy/blob/
 | `--cookie-secret` | string | the seed string for secure cookies (optionally base64 encoded) | |
 | `--cookie-secure` | bool | set [secure (HTTPS only) cookie flag](https://owasp.org/www-community/controls/SecureFlag) | true |
 | `--cookie-samesite` | string | set SameSite cookie attribute (`"lax"`, `"strict"`, `"none"`, or `""`). | `""` |
+| `--cookie-csrf-per-request` | bool | Enable having different CSRF cookies per request, making it possible to have parallel requests. | false |
+| `--cookie-csrf-expire` | duration | expire timeframe for CSRF cookie | 15m |
 | `--custom-templates-dir` | string | path to custom html templates | |
 | `--custom-sign-in-logo` | string | path or a URL to an custom image for the sign_in page logo. Use \"-\" to disable default logo. |
 | `--display-htpasswd-form` | bool | display username / password login form if an htpasswd file is provided | true |
@@ -595,4 +597,4 @@ http:
 
 :::note
 If you set up your OAuth2 provider to rotate your client secret, you can use the `client-secret-file` option to reload the secret when it is updated.
-:::
+:::