Limit window of Postgresql deprecation notice display
Problem to solve
Display the Postgresql upgrade deprecation notice a maximum of three releases in advance. Too far ahead and the notice will get ignored. Too little notice and admins won't be able to plan ahead.
Three is an arbitrary number I made as a best guess, corroborated by @ljlane
This is a spin off issue from !35271 (comment 372968049)
Intended users
User experience goal
User should receive an appropriate notice to upgrade Postgresql, but not so much time that it becomes ignored and fogotten.
Proposal
Only display the Postgresql deprecation notice banner within three months of the release that obsoletes the Postgresql version.