Frankly, I was hoping that the banner React component would be in core, however the PR is not there yet. Given the time constraints I will probably try to do the warning using our login page caption text.
I wonder if we should postpone dropping it by one release and make 1.24 the last version to support it. that will give users a bit longer time to plan their migration and us to test it and alert about it properly.
Alternatively, since the “browser support” PR (https://github.com/theforeman/foreman/pull/6776/files) is not a generic component yet, I can probably generate the warning banner using Rails/ERB. Disadvantage is that we want new components to be in React rather than plain ERB I guess. That’s why warning text on a login page (which is already in React) is more appealing to me.
Because we need a way to alert admins but not be too obtrusive, ie. allowing them to dismiss it. Perhaps using the notifications drawer would be good? We’ve done that in the past for deprecated settings - https://github.com/theforeman/foreman/pull/6038
IMHO the banner for MySQL is the wrong implementation. That’s needed for browser support because you can’t know it statically from the server side. With the database you do know and you can use the same notifications we used for orgs/locs. Exactly as @tbrisker wrote while I was typing this message.