modules/borgbackup: migrate to clanServices

Migrates the borgbackup module to clanServices, preserving it's original
configuration syntax and functionality

clanModules/borgbackup/README.md

@@ -1,7 +1,7 @@
 ---
 description = "Efficient, deduplicating backup program with optional compression and secure encryption."
 categories = ["System"]
-features = [ "inventory" ]
+features = [ "inventory", "deprecated" ]
 ---
 BorgBackup (short: Borg) gives you:
 

clanModules/borgbackup/roles/client.nix

@@ -106,7 +106,8 @@ in
     systemd.services = lib.mapAttrs' (
       _: dest:
       lib.nameValuePair "borgbackup-job-${dest.name}" {
-        # since borgbackup mounts the system read-only, we need to run in a ExecStartPre script, so we can generate additional files.
+        # since borgbackup mounts the system read-only, we need to run in a
+        # ExecStartPre script, so we can generate additional files.
         serviceConfig.ExecStartPre = [
           ''+${pkgs.writeShellScript "borgbackup-job-${dest.name}-pre-backup-commands" preBackupScript}''
         ];