* feat: allow msgIdProvider to fail
Closes: #642.
Changes the return type of the msgIdProvider to `Result[MessageID, string]` so that message id generation can fail.
String error type was chosen as this `msgIdProvider` mainly because the failed message id generation drops the message and logs the error provided. Because `msgIdProvider` can be externally provided by library consumers, an enum didn’t make sense and a object seemed to be overkill. Exceptions could have been used as well, however, in this case, Result ergonomics were warranted and prevented wrapping quite a large block of code in try/except.
The `defaultMsgIdProvider` function previously allowed message id generation to fail silently for use in the tests: when seqno or source peerid were not valid, the message id generated was based on a hash of the message data and topic ids. The silent failing was moved to the `defaultMsgIdProvider` used only in the tests so that it could not fail silently in applications.
Unit tests were added for the `defaultMsgIdProvider`.
* Change MsgIdProvider error type to ValidationResult
Eric Mastro