Create dedicated documentation page for users who land on Upsun 502 error page

[Kemi-Elizabeth]

Where on docs.platform.sh should be changed?

This page should be adapted: https://docs.upsun.com/development/troubleshoot.html#http-responses-502-bad-gateway-or-503-service-unavailable to include more direct and easy-to-understand troubleshooting solutions for users who are redirected here from an error 502 page.

What exactly should be updated?

Going to adapt this section to give users more actionable suggestions for troubleshooting when they are redirected to this page from an 502 error page.

Additional context

Linked Linear Issue: https://linear.app/platformsh/issue/ADV-1895/create-dedicated-documentation-page-for-users-who-land-on-upsun-502

Slack convo: https://platformsh.slack.com/archives/C088NDJ709Y/p1741708653544919