Mark ActivityExtensions.RecordException obsolete

[joegoldman2]

Activity.AddException will be added in .NET 9 (dotnet/runtime#53641). Should ActivityExtensions.RecordException then be deprecated?

[martinjt]

I'm not sure if we can do that anytime soon. It's probably valid, but a bit premature. since the adoption rate of .NET 9 will be slow (since it's not LTS), we'll need this for around 2 years at least.

If we develop a target for .NET 9 (I'm not sure if we will), it could be part of that.

We could look to update the docs, but even then it's going to be confusing for anyone not using .NET 9.

I think it should stay for a while, and it's not worth keeping an issue open for it until that happens.

[Kielek]

@martinjt, typically OTel SDK bumps System.DiagnosticsDiagnosticSource to the latest version. If this happen now, there should be no blocker to redirect users to use new API.

[cijothomas]

DS is out of band, so DS 9.0 can be used in any .NET versions, not just .NET 9. (OTel enforces that, as OTel always depend on the latest stable DS version.)

Deprecating ActivityExtensions.RecordException - this can be discussed during OTel 1.10 time, when it bumps to DS 9.0.

[Kielek]

@cijothomas, putting to 1.10.0 to do not forget about this.

[martinjt]

Totally my bad, .NET 9 threw me, completely forget it was in DS.