devdocs: Add notes on Python majors (#15053)

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## DESCRIBE YOUR PR

Clarify our philosophy for new majors and include specific steps to
consider when preparing a new major.

Direct link to preview:
https://develop-docs-git-ivana-devmajor.sentry.dev/sdk/platform-specifics/python-sdk/new-major/

Closes getsentry/sentry-python#4047

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## EXTRA RESOURCES

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<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> Adds a new docs page outlining considerations and concrete steps for
preparing a new major of the Python SDK.
> 
> - **Docs**:
> - **New page**:
`develop-docs/sdk/platform-specifics/python-sdk/new-major.mdx`
detailing:
> - Philosophy: prioritize migration ease, user-friendliness, and
backward compatibility.
> - Migration support: provide a dedicated migration guide with
copy-pastable examples; test AI-assisted upgrades.
> - Version support: guidance on dropping old Python/framework versions
using data; use `scripts/update_integration_support.py` to detect new
minimums.
> - Required updates: adjust `_MIN_VERSIONS` in
`sentry_sdk/integrations/__init__.py`, lower bounds in `extras_require`
in `setup.py`, and affected integration docs.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
e0b47dc. This will update automatically
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[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: sentrivana

develop-docs/sdk/platform-specifics/python-sdk/new-major.mdx

@@ -0,0 +1,30 @@
+---
+title: New Major
+description: What to consider when preparing a new major.
+sidebar_order: 50
+---
+
+Even if we decide to make a new major, it's important to prioritize user-friendliness, ease of migration, and backwards compatibility.
+
+Upgrading requires effort. Every major increases the chances of folks staying on an older version forever.
+
+Don't break existing APIs for a minor maintenance benefit on your end.
+
+
+## Making Migrating Easier
+
+Create a [migration guide](https://docs.sentry.io/platforms/python/migration/). Include easily understandable and copy-pastable examples wherever possible.
+
+Many folks might try to upgrade using AI. Try it out yourself on an example project. Consider adding rules specifically for migrating.
+
+
+## Dropping Version Support
+
+When making a new major, consider whether we should drop support for an old Python version. There is data in Looker you can use to make an informed decision.
+
+Investigate if we should drop support for old versions of frameworks and libraries. This is not feasible to do by hand as there's too many. For this purpose there is a small script in `scripts/update_integration_support.py` that automatically detects the effective lowest supported version based on our tests and package metadata. You can run the script after removing support for an old Python version, and it should automatically detect which minimum versions are no longer supported.
+
+In order to fully specify the new minimum versions:
+- Update `_MIN_VERSIONS` in `sentry_sdk/integrations/__init__.py`
+- Update the lower bounds in `extras_require` in `setup.py`, if specified
+- Update the documentation pages for the affected integrations (usually, the lowest supported version is mentioned at the bottom)