[FEATURE]: Add a custom tag to errors

[liaden]

Gem Name

No response

Gem Version(s)

No response

Describe the goal of the feature

Generically, I want to be able to add additional tags to allow for searching on errors.

Is your feature request related to a problem?

We have a monolith application with multiple teams supporting. Using the code_ownership, I want to add a team label where the value is CodeOwnership.for_backtrace(e).

Describe alternatives you've considered

1. Using Rails.error.handle to:
   a. Create a nested span with the appropriate tags to attach the error
   b. Do Datadog::Tracing.active_span.set_tag('error.team', team)
2. Using the on_error for some integrations (such as Sidekiq) to do the above, but there isn't one for Rails controllers (or Rack requests).
3. Monkeypatching Datadog::Tracing::Metadata::Errors#set_error_tags to attach the extra tags.

Additional context

No response

How does Datadog help you?

No response