Detect when the same attribute is referenced more than once

[lmolkova]

Describe the bug
build-tools had a check that prevented referencing the same attribute multiple times within one group.

e.g.

  - id: messaging.servicebus
    type: attribute_group
    extends: attributes.messaging.trace.minimal
    brief: >
      Attributes for Azure Service Bus
    attributes:
      - ref: messaging.operation.name
      - ref: messaging.operation.name
        brief: Azure Service Bus operation name.

caused an error like

Error parsing /source/trace/messaging.yaml:
Attribute id messaging.operation.name is already present at line 235 - @251:9 ('messaging.operation.name')

To Reproduce
See
open-telemetry/semantic-conventions@3c52fd0
and
https://github.com/open-telemetry/semantic-conventions/actions/runs/9230121422/job/25397692938?pr=1006

Expected behavior
table check done with weaver should detect it and complain (in the above CI check, it's still back-compat in semconv that raises an issue)

[jsuereth]

Can we make this a policy in: open-telemetry/semantic-conventions#1014?

Or should we consider this a core aspect of the model we enforce?

[lmolkova]

Can we make this a policy in: open-telemetry/semantic-conventions#1014 we make this a policy in: open-telemetry/semantic-conventions#1014?

I think it would be even better to define it as a policy in semconv

[lquerel]

Seems to be a good candidate for the policy engine.

[jsuereth]

Coming back to this - it DOES seem like the core model shouldn't allow two refs of the same thing. Going to mark this a bug but would like to either agree to fix in weaver or close as acceptable.

[lquerel]

@jsuereth Yes, I agree. That should be in the Weaver core model, and not in the policies as I mentioned several months ago.