Starting a span first migration guide so that we can use it for migrating Seer to span first (and eventually also for users undergoing the same migration).

This is still WIP.

Ref getsentry/sentry-python#5318

Direct link to preview: https://sentry-docs-git-ivana-span-first-migration-guide.sentry.dev/platforms/python/migration/span-first/

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SLA

• Teamwork makes the dream work, so please add a reviewer to your PRs.
• Please give the docs team up to 1 week to review your PR unless you've added an urgent due date to it.
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PRE-MERGE CHECKLIST

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• Checked Vercel preview for correctness, including links
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LEGAL BOILERPLATE

Look, I get it. The entity doing business as "Sentry" was incorporated in the State of Delaware in 2015 as Functional Software, Inc. and is gonna need some rights from me in order to utilize my contributions in this here PR. So here's the deal: I retain all rights, title and interest in and to my contributions, and by keeping this boilerplate intact I confirm that Sentry can use, modify, copy, and redistribute my contributions, under Sentry's choice of terms.

EXTRA RESOURCES

• Sentry Docs contributor guide