Add subcription feature 3

shared/exceptions/subscription_exceptions.py

@@ -0,0 +1,22 @@
+"""
+Subscription-related exceptions
+"""
+
+class SubscriptionException(Exception):
+    """Base class for subscription-related exceptions"""
+    pass
+
+class SubscriptionNotFound(SubscriptionException):
+    """Exception raised when subscription is not found"""
+    def __init__(self, message: str = "Subscription not found"):
+        super().__init__(message)
+
+class SubscriptionAlreadyExists(SubscriptionException):
+    """Exception raised when subscription already exists"""
+    def __init__(self, message: str = "Subscription already exists"):
+        super().__init__(message)
+
+class SubscriptionUpdateFailed(SubscriptionException):
+    """Exception raised when subscription update fails"""
+    def __init__(self, message: str = "Subscription update failed"):
+        super().__init__(message)