Performance instrumentation for Sanic Integration

[antonpirker]

Problem Statement

Currently the SanicIntegration does not start transactions for a request-response-cycle.

Solution Brainstorm

If Sanic is a WSGI based framework we maybe can use SentryWsgiMiddleware like bottle does:
https://github.com/getsentry/sentry-python/blob/master/sentry_sdk/integrations/bottle.py

If not we can have a look at how the low level WSGI integration creates transactions (and continues traces from incoming requests): https://github.com/getsentry/sentry-python/blob/master/sentry_sdk/integrations/wsgi.py#L97-L115