Organize UserOperation data types (#819)

* Add missing address to the mock
* Make paymaster data return optional

gnosis/eth/account_abstraction/user_operation.py

@@ -77,8 +77,9 @@ def paymaster(self) -> Optional[ChecksumAddress]:
         return None
 
     @cached_property
-    def paymaster_data(self) -> bytes:
-        return self.paymaster_and_data[:20]
+    def paymaster_data(self) -> Optional[bytes]:
+        result = self.paymaster_and_data[:20]
+        return result if result else None
 
     def calculate_user_operation_hash(self, chain_id: int) -> bytes:
         hash_init_code = fast_keccak(self.init_code)

gnosis/eth/tests/mocks/mock_bundler.py

@@ -1,6 +1,10 @@
+from eth_typing import ChecksumAddress, HexAddress, HexStr
 from hexbytes import HexBytes
 
 # Module address and chainId used for the following mocks
+safe_4337_address = ChecksumAddress(
+    HexStr(HexAddress("0xB0B5c0578Aa134b0496a6C0e51A7aae47C522861"))
+)
 safe_4337_user_operation_hash_mock = HexBytes(
     "0x39b3e2171c04539d9b3f848d04364dfaa42cc0b412ff65ce2a85c566cf8bf281"
 )