add doc for Zitadel configuration (#221)

* add doc for Zitadel configuration

Add instructions to set up Zitadel

* add link from configuration doc

docs/configuration.md

@@ -22,6 +22,7 @@ Here are some documentation links for specific providers that you may want to fo
 * [Pocket ID](./provider-configurations/pocket-id.md)
 * [Kanidm](./provider-configurations/kanidm.md)
 * [Microsoft Entra ID](./provider-configurations/microsoft-entra.md)
+* [Zitadel](./provider-configurations/zitadel.md)
 
 _Missing a provider? Submit your guide using a PR._
 

docs/provider-configurations/zitadel.md

@@ -0,0 +1,27 @@
+# Zitadel
+
+## Zitadel configuration
+
+1. From the Zitadel home screen, go to `Projects` and click `Create New Project`
+2. Enter "Home Assistant" or your preferred name
+3. Click on `New` to create a new Application
+4. Enter "Home Assistant" or your preferred name
+5. Select `Web` and `Continue`
+6. Select `CODE` (not `PKCE`) and `Continue`
+7. Enter https://hass.example.com/auth/oidc/callback as the Redirect URI, and click `Continue`
+8. Click `Create`. A pop-up will dispay the `ClientId` and `ClientSecret`
+
+## Home Assistant configuration
+
+> [!IMPORTANT]  
+> For HTTPS configuration make sure to have a public valid SSL certificate (i.e. LetsEncrypt), if not, use HTTP instead (more insecure) or add your Zitadel CA certificate to `network.tls_ca_path`.
+
+After installing this HACS addon, edit your `configuration.yaml` file and add:
+```yaml
+auth_oidc:
+  client_id: <ClientID from above>
+  client_secret: <ClientSecret from above>
+  discovery_url: "https://auth.example.com/.well-known/openid-configuration"
+```
+
+Restart Home Assistant and go to https://hass.example.com/auth/oidc/welcome