Don't ignore constraints in redirect routes

https://github.com/rails/rails/commit/402c2af55053c2f29319091ad21fd6fa6b90ee89
introduced a regression that caused any constraints added to redirect routes
to be ignored.

Fixes #16605
No transaction for a test that creates fixtures in the test body
Avoid using heredoc for user warnings

Using heredoc would enforce line wrapping to whatever column width we decided to
use in the code, making it difficult for the users to read on some consoles.

This does make the source code read slightly worse and a bit more error-prone,
but this seems like a fair price to pay since the primary purpose for these
messages are for the users to read and the code will not stick around for too
long.
Merge pull request #16637 from Agis-/redirect-with-constraint-route

Fix the router ignoring constraints when used together with a redirect route
Active Job refactoring