MongoDB: Document "undefined" behavior

[matthewmueller]

We're making some changes in 3.11.1 around how records with undefined are queried

This internal document has the details.

I asked Dom for a bit of clarity:

Suggestion:

• Release notes or small docs page on breaking changes in the upgrade (undefineds are now ignores)
• Document isSet as a new query operation
• Document that undefined values in MongoDB are not matched by default, you use isSet to match them.

[tanberry]

Docs impacted by 3.11.1 patch release:
ASAP:
--https://www.prisma.io/docs/concepts/components/prisma-client/null-and-undefined (PR #3009)
-- https://www.prisma.io/docs/concepts/components/prisma-client/filtering-and-sorting
--https://www.prisma.io/docs/reference/api-reference/prisma-client-reference#filter-conditions-and-operators

Later polishing:
-- https://www.prisma.io/docs/reference/api-reference/prisma-client-reference#event-types ("Note that for MongoDB, the params and duration fields will be undefined.")
-- a lot of the troubleshooting topics

[matthewmueller]

Closed by: #3017