Custom kernel message serializer

[DonJayamanne]

References

Fixes #15198

Code changes

Exposes the message serializer in the ISettings, allowing one to customize how messages are serialized/deserialized based on the server (settings).

User-facing changes

N/A

Backwards-incompatible changes

N/A

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[krassowski]

Thanks @DonJayamanne, this looks good to me!

[DonJayamanne]

@krassowski
Should I mark this as ready for review, or is there something else we need?
I do not think we need tests for this change, and the docs are generated from the ts code.

[krassowski]

Addding a unit test ensuring that the serializer can actually be changed can help catch regression if this function gets rewritten (all it takes to break it is to move ...options one line up) so it could benefit you in the future. Other than that no follow up tasks here.

[fcollonval]

Thanks @DonJayamanne

I agree that it will be nice to test providing custom de/serializers in a test.