plugin XEP-0384: fix trigger used for OLDMEMO: OLDMEMO was applied at the `send_message_data` trigger level, however this was missing stanza constructed without message data (which is notably the case for XEP-0308). This has been fixed by using the `send` trigger instead. As a side effect, the same code is now used for TWOMEMO and OLDMEMO, making it simpler.

from typing import Optional

from twisted.words.xish import domish


class BaseError(Exception):
    namespace: str
    condition: str
    text: Optional[str]
    textLang: Optional[str]
    appCondition: Optional[domish.Element]

class StanzaError(BaseError):
    ...