Can we set the root cause of exception in metrics?

[chao-chang-paypay]

Setting the root cause(e.g. SocketTimeoutException ) as the tag value might be more helpful than the exception in feign layer(e.g. RetryableException)

feign/micrometer/src/main/java/feign/micrometer/FeignMetricTagResolver.java

Line 52 in 5b8cd4a

tags.add(Tag.of("exception_name", e.getClass().getSimpleName()));

[velo]

That makes a lot of sense, feel free to make a PR for this change.

Cheers,