Start to implement posts creation

src/helpers/groups_helper.rs

@@ -414,6 +414,17 @@ pub fn respond_request(group_id: &GroupID, user_id: &UserID, accept: bool) -> Re
     }
 }
 
+/// check out whether a user can create posts on a group or not
+pub fn can_user_create_posts(group_id: &GroupID, user_id: &UserID) -> ResultBoxError<bool> {
+    let membership_level = get_membership_level(group_id, user_id.as_option())?;
+
+    match membership_level {
+        GroupMembershipLevel::ADMINISTRATOR | GroupMembershipLevel::MODERATOR => Ok(true),
+        GroupMembershipLevel::MEMBER => Ok(get_info(group_id)?.posts_creation_level == GroupPostsCreationLevel::POSTS_LEVEL_ALL_MEMBERS),
+        _ => Ok(false),
+    }
+}
+
 /// Turn a database entry into a group struct
 fn db_to_group(row: &database::RowResult) -> ResultBoxError<Group> {
     let group_id = row.get_group_id("id")?;