sway/swaynag: Deduplicate config

users/simon/modules/sway.nix

@@ -270,24 +270,27 @@ lib.mkIf nixosConfig.sbruder.gui.enable {
     wdisplays # graphical output manager
   ];
 
-  # FIXME deduplicate (everything except text is redundant)
-  xdg.configFile."swaynag/config".text = ''
-    font=Monospace 12
+  xdg.configFile."swaynag/config".text =
+    let
+      # adding it to the header doesn’t work since the defaults overwrite it
+      commonConfig = ''
+        background=fdf6e3
+        border-bottom=eee8d5
+        border=eee8d5
+        button-background=eee8d5
+      '';
+    in
+    ''
+      font=Monospace 12
 
-    [warning]
-    text=b58900
-    background=fdf6e3
-    border=eee8d5
-    border-bottom=eee8d5
-    button-background=eee8d5
+      [warning]
+      text=b58900
+      ${commonConfig}
 
-    [error]
-    text=dc322f
-    background=fdf6e3
-    border=eee8d5
-    border-bottom=eee8d5
-    button-background=eee8d5
-  '';
+      [error]
+      text=dc322f
+      ${commonConfig}
+    '';
 
   # home-manager’s waybar module performs additional checks that are overly strict
   xdg.configFile."waybar/config".text =