After upgrading to the latest major version of mongodb.driver, we discovered a breaking change that is not documented in the Release Notes or the Breaking Changes section.

Issue:
As part of CSHARP-3717, a new serializer for the TimeOnly type was introduced. However, documents serialized using the previous driver version can no longer be deserialized by the new version. This introduces a breaking change in backward compatibility, but there is no mention of this in the Release Notes or Breaking Changes documentation.

Expected:

• The breaking change should be clearly documented in either the "How to Upgrade" guide or the "Breaking Changes" section.
• Alternatively, the new serializer should provide a backward compatibility mode that allows it to correctly read documents serialized by the previous version.