feat(instrumentation-anthropic): Support for OpenTelemetry metrics for Anthropic

[hanchchch]

relates to #251

Hi,

I referred a lot to #369 while working on this.

I added

• token_counter
• choice_counter
• duration_histogram
• exception_counter

metrics for all

• sync / async
• completion / messages / streaming messages

methods.

There are a few TODOs, I'd appreciate it if you check it out.

• One is about adding choice_counter of streaming response, I just added length of events bc each of it has finish_reason, but I'm still not sure if it's appropriate. (opentelemetry/instrumentation/anthropic/streaming.py).
• The others are about testing exception_metric of streaming responses. I think I should add mocks and trigger exception in the middle of yielding, but I'm just wondering if there's better way. (tests/test_completion.py)

Any comments and discussions will be appreciated!

---

• I have added tests that cover my changes.
• If adding a new instrumentation or changing an existing one, I've added screenshots from some observability platform showing the change.
• PR name follows conventional commits format: feat(instrumentation): ... or fix(instrumentation): ....
• (If applicable) I have updated the documentation accordingly.

[nirga]

Thanks @hanchchch! Great work! Looks good.
Note that you need to rebase your PR. Once you do that I can merge :)