Feature: Support "does-not-contain" as operator

[tr-fteixeira]

Hello,

Seems like not all ui/api operators from the platform are supported on the RuleBasedSampler, here.

When using one of the unsupported operators, there is no indication of error, it just doesn't match the desired trace/span.
It is also not documented anywhere (that i could find).

Im looking specifically for that one, but would be nice to have them all =)

Regards,

[MikeGoldsmith]

Closing this issue now #267 was merged. #266 will be use to track enhanced rules validation.