feat: add models part 3

itd/exceptions.py

@@ -48,4 +48,14 @@ class RateLimitExceeded(Exception):
     def __init__(self, retry_after: int):
         self.retry_after = retry_after
     def __str__(self):
-        return f'Rate limit exceeded - too much requests. Retry after {self.retry_after} seconds'
+        return f'Rate limit exceeded - too much requests. Retry after {self.retry_after} seconds'
+
+class Forbidden(Exception):
+    def __init__(self, action: str):
+        self.action = action
+    def __str__(self):
+        return f'Forbidden to {self.action}'
+
+class UsernameTaken(Exception):
+    def __str__(self):
+        return 'Username is already taken'