Add InvalidId as valid error in bson exports

[nadavge]

It is "impossible" (or unconventional) to catch exceptions for an invalid ID, even though there's no good reason not to IMHO.

[juliusgeo]

@nadavge Hi, I appreciate you opening this PR. That error is already importable--the following code for me runs fine on PyMongo 4.1 with Python 3.8.12 (in a new venv).

from bson.errors import InvalidId
try:
        pass
except InvalidId:
        # Handle exception
        pass

The only thing that your change allows is importing from the package namespace like so:

From bson import InvalidId

All of the other errors that are imported in bson/__init__.py are also used in that same file--hence the import. I believe that users are intended to import from bson.errors based on the PyMongo BSON documentation for errors.
Could I ask for the specific reason why you wish it to be in the packages namespace?

[pooooodles]

We're closing this out since we haven't heard anything further in this thread, but please let us know if you'd like to continue the conversation!