It should be possible to let service clients set the schema URL in the future.

it's not an immediate need, but it should be possible to add the schema URL in the future.

Now it can be a singleton and can be hardcoded in the core, but it won't be the case the moment instrumentation adds a custom attribute - if core updates to vZ, old library versions instrumentations reporting vX will start lying.

Hand-written instrumentations will inevitably have different versions - e.g. cosmos follows vX and servicebus follows vY.
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_Originally posted by @lmolkova in https://github.com/Azure/azure-sdk-for-rust/pull/2741#discussion_r2219835733_

The issue names no files or tests; start by reading the discussion in PR #2741 and tracing how the core currently provides the schema URL to service clients and instrumentation. Done should mean the design clearly supports client- or instrumentation-specific schema URLs without older instrumentation reporting a mismatched version.

Written by the indexing model from the issue text.