website/docs: add architecture and persistence (#6250)

* website/docs: add architecture and persistence

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

* Apply suggestions from code review

Co-authored-by: Tana M Berry <tanamarieberry@yahoo.com>
Signed-off-by: Jens L. <jens@beryju.org>

* Apply suggestions from code review

Co-authored-by: Tana M Berry <tanamarieberry@yahoo.com>
Signed-off-by: Jens L. <jens@beryju.org>

* add note about kubernetes

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

* link to relevant parts

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

---------

Signed-off-by: Jens Langhammer <jens@goauthentik.io>
Signed-off-by: Jens L. <jens@beryju.org>
Co-authored-by: Tana M Berry <tanamarieberry@yahoo.com>

website/docs/core/architecture.md

@@ -0,0 +1,61 @@
+---
+title: Architecture
+---
+
+authentik consists of a handful of components, most of which are required for a functioning setup.
+
+```mermaid
+graph LR
+    user(User) --> ak_server(authentik Server)
+    ak_server --> ak_server_core(authentik Server Core)
+    ak_server --> ak_outpost(Embedded outpost)
+    ak_server_core --> db(PostgreSQL)
+    ak_server_core --> cache(Redis)
+    ak_worker(Background Worker) --> db(PostgreSQL)
+    ak_worker(Background Worker) --> cache(Redis)
+```
+
+### Server
+
+The server container consists of two sub-components, the actual server itself and the embedded outpost. Incoming requests to the server container(s) are routed by a lightweight router to either the _Core_ server or the embedded outpost. This router also handles requests for any static assets such as JavaScript and CSS files.
+
+#### Core
+
+The core sub-component handles most of authentik's logic, such as API requests, flow executions, any kind of SSO requests, etc.
+
+#### Embedded outpost
+
+Similar to [other outposts](../outposts/index.mdx), this outposts allows using [Proxy providers](../providers/proxy/index.md) without deploying a separate outpost.
+
+#### Persistence
+
+-   `/media` is used to store icons and such, but not required, and if not mounted, authentik will allow you to set a URL to icons in place of a file upload
+
+### Background Worker
+
+This container executes background tasks, such as sending emails, the event notification system, and everything you can see on the _System Tasks_ page in the frontend.
+
+#### Persistence
+
+-   `/certs` is used for authentik to import external certs, which in most cases shouldn't be used for SAML, but rather if you use authentik without a reverse proxy, this can be used for example for the [Let's Encrypt integration](../core/certificates.md#lets-encrypt)
+-   `/templates` is used for [custom email templates](../flow/stages/email/index.mdx#custom-templates), and as with the other ones fully optional
+
+### PostgreSQL
+
+authentik uses PostgreSQL to store all of its configuration and other data (excluding uploaded files).
+
+#### Persistence
+
+-   `/var/lib/postgresql/data` is used to store the PostgreSQL database
+
+On Kubernetes, with the default Helm chart and using the packaged PostgreSQL sub-chart, persistent data is stored in a PVC.
+
+### Redis
+
+authentik uses Redis as a message-queue and a cache. Data in Redis is not required to be persistent, however you should be aware that restarting Redis will cause the loss of all sessions.
+
+#### Persistence
+
+-   `/data` is used to store the Redis data
+
+On Kubernetes, with the default Helm chart and using the packaged Redis sub-chart, persistent data is stored in a PVC.

website/docs/installation/docker-compose.md

@@ -71,6 +71,13 @@ See [Configuration](../installation/configuration) to change the internal ports.
 
 ## Startup
 
+:::warning
+The server assumes to have local timezone as UTC.
+All internals are handled in UTC; whenever a time is displayed to the user in UI, the time shown is localized.
+Do not update or mount `/etc/timezone` or `/etc/localtime` in the authentik containers.
+This will not give any advantages. It will cause problems with OAuth and SAML authentication, e.g. [see this GitHub issue](https://github.com/goauthentik/authentik/issues/3005).
+:::
+
 Afterwards, run these commands to finish:
 
 ```shell
@@ -85,28 +92,3 @@ By default, authentik is reachable (by default) on port 9000 (HTTP) and port 944
 To start the initial setup, navigate to `https://<your server's IP or hostname>:9000/if/flow/initial-setup/`.
 
 There you are prompted to set a password for the akadmin user (the default user).
-
-## Explanation
-
-:::warning
-The server assumes to have local timezone as UTC.
-All internals are handled in UTC; whenever a time is displayed to the user in UI it gets localized.
-Do not update or mount `/etc/timezone` or `/etc/localtime` in the authentik containers.
-This will not give any advantages.
-On the contrary, it will cause problems with OAuth and SAML authentication,
-e.g. [see this GitHub issue](https://github.com/goauthentik/authentik/issues/3005).
-:::
-
-The Docker-Compose project contains the following containers:
-
--   server
-
-    This is the backend service, which does all the logic, plus runs the API and the SSO functionality. It also runs the frontend, hosts the JS/CSS files, and serves the files you've uploaded for icons/etc.
-
--   worker
-
-    This container executes background tasks, everything you can see on the _System Tasks_ page in the frontend.
-
--   redis (for cache)
-
--   postgresql (default database)

website/sidebars.js

@@ -33,6 +33,7 @@ module.exports = {
                 "core/tenants",
                 "core/certificates",
                 "core/geoip",
+                "core/architecture",
             ],
         },
         {