Added Synology DSM integration

website/integrations/services/synology-dsm/index.md

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+---
+title: Synology DSM
+---
+
+<span class="badge badge--secondary">Support level: Community</span>
+
+## What is Synology DSM
+
+> Synology Inc. is a Taiwanese corporation that specializes in network-attached storage (NAS) appliances. Synology's line of NAS is known as the DiskStation for desktop models, FlashStation for all-flash models, and RackStation for rack-mount models. Synology's products are distributed worldwide and localized in several languages.
+>
+> -- https://www.synology.com/en-global/dsm
+
+:::caution
+This is tested with DSM 7.1 or newer.
+:::
+
+## Preparation
+
+The following placeholders will be used:
+
+-   `synology.company` is the FQDN of the Synology DSM server.
+-   `authentik.company` is the FQDN of the authentik install.
+
+### Step 1
+
+Under _Providers_, create an OAuth2/OpenID provider with these settings:
+
+-   Name: synology
+-   Redirect URI: `https://synology.company/#/signin` (Note the absence of the trailing slash, and the inclusion of the webinterface port)
+-   Signing Key: Select any available key
+-   Subject mode: Based on the Users's Email (Matching on username could work, but not if you have duplicates due to e.g. a LDAP connection)
+-   Take note of the 'Client ID' and 'Client secret'
+
+### Step 2
+
+Create an application which uses this provider. Optionally apply access restrictions to the application.
+
+## Synology DSM setup
+
+To configure Synology DSM to utilize Authelia as an OpenID Connect 1.0 Provider:
+
+1. Go to DSM.
+2. Go to Control Panel.
+3. Go To Domain/LDAP.
+4. Go to SSO Client.
+5. Check the Enable OpenID Connect SSO service checkbox in the OpenID Connect SSO Service section.
+6. Configure the following values:
+7. Profile: OIDC
+8. Name: Authentik
+9. Well Known URL: Copy this from the 'OpenID Configuration URL' in the authentik provider (URL ends with '/.well-known/openid-configuration')
+10. Application ID: The 'Client ID' from the authentik provider
+11. Application Key: The 'Client secret' from the authentik provider
+12. Redirect URL: https://synology.company/#/signin (This should match the 'Redirect URI' in authentik exactly)
+13. Authorization Scope: openid profile email
+14. Username Claim: preferred_username
+15. Save the settings.
+
+
+## See also:
+[Synology DSM SSO Client Documentation](https://kb.synology.com/en-af/DSM/help/DSM/AdminCenter/file_directory_service_sso?version=7)