Expected Behavior

As a user of js-bson
I expect only written bytes of a Binary to be encoded
When calling toExtendedJSON

Actual Behavior and Impact

• calling toExtendedJSON will base64 document values representing the full underlying buffer for binary types, not just the data therein.
• No known customer reports today.

Dependencies

• None

Risks/Unknowns

• Any consumer that was inadvertently relying on the padded base64 output (e.g., reading the full 256-byte allocation) would see a breaking change in serialized output.

Acceptance Criteria

Implementation Requirements

• Base64 of a binary should be representative of only the portion of the buffer that actually has data (IE: respect the 'position')

Testing Requirements

• None (already present in the external PR)

Documentation Requirements

• None

Follow Up Requirements

• None