flarum module: define package config, use in config

Signed-off-by: Jack Leightcap <jack@leightcap.com>

modules/flarum.nix

@@ -39,6 +39,8 @@ in
     services.flarum = {
       enable = mkEnableOption "Flarum discussion platform";
 
+      package = mkPackageOptions pkgs "flarum" {};
+
       forumTitle = mkOption {
         type = types.str;
         default = "A Flarum Forum on NixOS";
@@ -155,7 +157,7 @@ in
         extraConfig =
           ''
             index index.php;
-            include ${pkgs.flarum}/.nginx.conf;
+            include ${cfg.package}/.nginx.conf;
           '';
       };
     };
@@ -192,9 +194,9 @@ in
         mkdir -p ${cfg.stateDir}/{extensions,public/assets/avatars}
         mkdir -p ${cfg.stateDir}/storage/{formatter,sessions,views}
         cd ${cfg.stateDir}
-        cp -f ${pkgs.flarum}/{extend.php,site.php,flarum} .
-        ln -sf ${pkgs.flarum}/vendor .
-        ln -sf ${pkgs.flarum}/public/index.php public/
+        cp -f ${cfg.package}/{extend.php,site.php,flarum} .
+        ln -sf ${cfg.package}/vendor .
+        ln -sf ${cfg.package}/public/index.php public/
         chmod a+x . public
       '' + lib.optionalString (cfg.createDatabaseLocally && cfg.database.driver == "mysql") ''
         cp ${flarumInstallConfig} .