Support setting the serde modes through toJson/fromJson calls

[AuHau]

Sometimes you have type that you would like to serialize/deserialize which you don't have control over (for example coming from library). Currently, I don't know of a way how to achieve that. I would hence propose for adding a parameter to the toJson() and fromJson() calls that would allow setting the Serde's mode. In this way, I could set it to SerdeMode.OptOut and be able to serialize it.

[emizzle]

Good idea!