Some APIs of Builder do not add the timestamp

[duggaraju]

Component

c2pa-rs

If Other, please specify

Builder

Version

v0.84.0

Platform

Linux

What happened?

c2pa_builder_sign() uses builder.sign() which calls maybe_add_timestamp().
However c2pa_builder_sign_context() calls builder.save_to_stream() which doesn't call maybe_add_timestamp() and hence doesn't add the timesatmp.

What did you expect to happen?

Using context should use the signer /settings from context but the rest of the builder behavior should be consistent across APIs.