providers/proxy: outpost wide logout implementation (#4605)

* initial outpost wide logout implementation

Signed-off-by: Jens Langhammer <jens@goauthentik.io>

* handle deserialize error

Signed-off-by: Jens Langhammer <jens@goauthentik.io>

* update docs

Signed-off-by: Jens Langhammer <jens@goauthentik.io>

* fix file cleanup, add tests

Signed-off-by: Jens Langhammer <jens@goauthentik.io>

* fix tests

Signed-off-by: Jens Langhammer <jens@goauthentik.io>

---------

Signed-off-by: Jens Langhammer <jens@goauthentik.io>

website/docs/releases/2023/v2023.2.md

@@ -0,0 +1,34 @@
+---
+title: Release 2023.2
+slug: "/releases/2023.2"
+---
+
+## New features
+
+-   Proxy provider logout improvements
+
+    In previous versions, logging out of a single proxied application would only invalidate that application's session. Starting with this release, when logging out of a proxied application (via the _/outpost.goauthentik.io/sign_out_ URL), all the users session within the outpost are terminated. Sessions in other outposts and with other protocols are unaffected.
+
+## Upgrading
+
+This release does not introduce any new requirements.
+
+### docker-compose
+
+Download the docker-compose file for 2023.2 from [here](https://goauthentik.io/version/2023.2/docker-compose.yml). Afterwards, simply run `docker-compose up -d`.
+
+### Kubernetes
+
+Update your values to use the new images:
+
+```yaml
+image:
+    repository: ghcr.io/goauthentik/server
+    tag: 2023.2.0
+```
+
+## Minor changes/fixes
+
+## API Changes
+
+_Insert output of `make gen-diff` here_