Allow Flask instrumentation to filter on paths

The FlaskInstrumentor accepts an excluded_urls parameter, which takes a sequence of regular expressions that it compares against

flask.request.url, here:

https://github.com/open-telemetry/opentelemetry-python-contrib/blob/main/instrumentation/opentelemetry-instrumentation-flask/src/opentelemetry/instrumentation/flask/__init__.py#L192

In my opinion it would be nicer to be able to filter on the path instead (flask.request.path), at least in some cases.

For instance, if you want to disable tracing on the root path (so just /), that's relatively easy to do if you filter on path (with the regular expression^/$), but becomes a massive pain if you have to take the whole url into account.

It's probably too late to change the meaning of excluded_urls, but would it be possible to add an optional excluded_paths parameter?

If there's a chance that it would be accepted, I'd be happy to work on an implementation.

Start in instrumentation/opentelemetry-instrumentation-flask/src/opentelemetry/instrumentation/flask/init.py at the excluded_urls handling around line 192. Trace how the existing URL filter is configured and applied, then determine how an optional excluded_paths filter should use flask.request.path while preserving excluded_urls behavior. Done means path-based filtering works for cases such as ^/$ and existing URL filtering remains compatible.