add ID field to post dto

dto/post.py

@@ -1,10 +1,13 @@
 class Post:
-    def __init__(self, author: str, 
+    def __init__(self, 
+                 id: str,
+                 author: str, 
                  title: str, 
                  content: str, 
                  url: str, 
                  timestamp: float, 
                  source: str):
+        self.id = id
         self.author = author
         self.title = title
         self.content = content