Added note about breaking changes in 10.0.0

[cmeeren]

Changing the default serializer is a breaking change and should be explicitly called out.

We were hit by outages in production because while I had carefully reviewed the changelog, this particular change was not mentioned, and therefore not tested. (Shame on us for not having a sufficiently comprehensive test suite to catch this, of course.)

[abatishchev]

An outage in production? Oh no! I'm sorry to hear/cause this, my apologies for not calling it out clearly. I'll update the changelog accordingly, thanks for the contribution!

For my better understanding, can you explain what was the scenario and how it got broken?

[cmeeren]

I'm sorry to hear/cause this

Again, not your fault. Shame on us for not having a sufficiently comprehensive test suite to catch this. Btw if it were mentioned in the changelog, I would likely have checked a few more things manually and caught this, which is why I'm adding it. 🙂

For my better understanding, can you explain what was the scenario and how it got broken?

I parsed the token to Dictionary<string, obj> and cast relevant payload items to string when getting them from the dictionary. Not sure why I went with that solution originally, but it worked, because apparently Newtonsoft.Json deserializes to a suitable underlying type when using obj. However, System.Text.Json deserialized to JsonElement or something like that, which made the code fail due to invalid cast.

I now use the non-generic Decode overload and deserialize the JSON myself using my own serialization settings.