Document S3 permission requirements

[acdha]

The S3 configuration requires slightly non-obvious permissions because the default ACL setting is public-read, which means that PutObject will fail unless you also have the PutObjectAcl permission.

It looks like there may be a way to set the default ACL to private which would avoid this but I have not yet been able to confirm it works:

getsentry/sentry#11033

[github-actions]

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: Accepted, I will leave it alone ... forever!

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