Return NoOpSpans when transaction finished

[philipphofmann]

Problem Statement

Related to https://github.com/getsentry/sentry-java/issues/1840

Solution Brainstorm

After calling finish, the transaction should return a NoOpSpan and log a message that the SDK is not sending the span to Sentry.

[github-actions[bot]]

This issue has gone three weeks without activity. In another week, I will close it.

But! If you comment or otherwise update it, I will reset the clock, and if you label it Status: Backlog or Status: In Progress, I will leave it alone ... forever!

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"A weed is but an unloved flower." ― Ella Wheeler Wilcox 🥀