nixos/nginx: add extraConfigPre option for locations

nixos/modules/services/web-servers/nginx/default.nix

@@ -528,6 +528,7 @@ let
     concatStringsSep "\n" (
       map (config: ''
         location ${config.location} {
+          ${config.extraConfigPre}
           ${optionalString (
             config.proxyPass != null && !cfg.proxyResolveWhileRunning
           ) "proxy_pass ${config.proxyPass};"}

nixos/modules/services/web-servers/nginx/location-options.nix

@@ -131,6 +131,14 @@ with lib;
       '';
     };
 
+    extraConfigPre = mkOption {
+      type = types.lines;
+      default = "";
+      description = ''
+        These lines go to the beginning of the location verbatim.
+      '';
+    };
+
     priority = mkOption {
       type = types.int;
       default = 1000;