website/docs: add matrix docs

closes #1477

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

website/docs/integrations/services/matrix-synapse/index.md

@@ -0,0 +1,50 @@
+---
+title: Matrix Synapse
+---
+
+## What is Matrix Synapse
+
+From https://matrix.org/
+
+:::note
+Matrix is an open source project that publishes the Matrix open standard for secure, decentralised, real-time communication, and its Apache licensed
+reference implementations.
+:::
+
+## Preparation
+
+The following placeholders will be used:
+
+- `matrix.company` is the FQDN of the MinIO install.
+- `authentik.company` is the FQDN of the authentik install.
+
+Create an application in authentik. Create an OAuth2/OpenID provider with the following parameters:
+
+- Client Type: `Confidential`
+- JWT Algorithm: `RS256`
+- Scopes: OpenID, Email and Profile
+- RSA Key: Select any available key
+- Redirect URIs: `https://matrix.company/_synapse/client/oidc/callback`
+
+Note the Client ID and Client Secret values. Create an application, using the provider you've created above. Note the slug of the application you've created.
+
+## Matrix
+
+Add the following block to your Matrix config
+
+```yaml
+oidc_providers:
+  - idp_id: authentik
+    idp_name: authentik
+    discover: true
+    issuer: "https://authentik.company/application/o/app-slug/"
+    client_id: "*client id*"
+    client_secret: "*client secret*"
+    scopes:
+      - "openid"
+      - "profile"
+    user_mapping_provider:
+      config:
+        localpart_template: "{{ '{{ user.name }}' }}"
+        display_name_template: "{{ '{{ user.name|capitalize }}' }}"
+```

website/sidebars.js

@@ -87,6 +87,7 @@ module.exports = {
                         "integrations/services/grafana/index",
                         "integrations/services/harbor/index",
                         "integrations/services/home-assistant/index",
+                        "integrations/services/matrix-synapse/index",
                         "integrations/services/minio/index",
                         "integrations/services/nextcloud/index",
                         "integrations/services/portainer/index",