Move Bookwyrm systemd unit from package to NixOS module

bookwyrm.nix

@@ -116,17 +116,6 @@ mkDerivation {
 
 		chmod +x $out/bin/bookwyrm
 
-		# Systemd units
-
-		cat <<- EOF > $out/lib/systemd/system/bookwyrm.service
-			[Unit]
-			After=network.target
-
-			[Service]
-			ExecStart=$out/bin/bookwyrm
-			WorkingDirectory=/var/lib/bookwyrm
-		EOF
-
 		runHook postInstall
 	'' ;
 }

nixos-module.nix

@@ -51,4 +51,19 @@
 			)
 		] ;
 	} ;
+
+	systemd = {
+		units = {
+			bookwyrm = {
+				text = ''
+					[Unit]
+					After=network.target
+
+					[Service]
+					ExecStart=$out/bin/bookwyrm
+					WorkingDirectory=/var/lib/bookwyrm
+				'' ;
+			} ;
+		} ;
+	} ;
 }