[@loopback/sequelize] Regression in query behavior when undefined values passed to "where" filter

[KalleV]

Describe the bug

I noticed passing "undefined" to a where filter value will lead to a "NULL" query internally. This causes issues with backward compatibility for application business logic using optional values since the Juggler ORM omits "undefined" values from the internal SQL queries.

Original connector logic that skips over undefined can be found here: https://github.com/loopbackio/loopback-connector/blob/62a9fd10ddf896c874ca7a80a9fd4a472d303637/lib/sql.js#L1194-L1196

Example

With the Sequelize extension:

const userData = await userRepo.find({
  where: {name: user.name, email: user.email, password: undefined},
});

This leads to a query such as:

SELECT ... WHERE ..., password = NULL

Logs

No response

Additional information

No response

Reproduction

https://github.com/loopbackio/loopback-next/pull/10128/files