Can update posts visibility levels

lib/helpers/posts_helper.dart

@@ -69,6 +69,19 @@ class PostsHelper {
         .isOK;
   }
 
+  /// Update a post visibility
+  Future<bool> setVisibility(int id, PostVisibilityLevel level) async {
+    return (await APIRequest(
+      uri: "posts/set_visibility_level",
+      needLogin: true,
+      args: {
+        "postID": id.toString(),
+        "new_level": _APIPostsVisibilityLevelMap.map((k, v) => MapEntry(v, k))[level]
+      },
+    ).exec())
+        .isOK;
+  }
+
   /// Delete a post
   Future<bool> delete(int id) async {
     return (await APIRequest(