Summary

Distinguish "null" and "{}" in URI test runner assertions.

Background & Motivation

See slack thread.

The C driver URI test runner runs tests for the Connection String spec, Auth spec, and URI Options spec.

The test runner uses bson_lookup_doc_null_ok to look-up expectations for "auth", "credentials", "hosts", and "options".

The Connection String spec and URI Options spec note:

If a test case includes a null value for one of these keys (e.g. auth: ~, port: ~), no assertion is necessary.

The Auth spec notes:

credential: If null, the credential must not be considered configured