refs https://ghost.slack.com/archives/C02G9E68C/p1647599592576139
When you add a redirect multiple times, and remove it afterwards, an error is thrown:
`Cannot destructure property 'fromRegex' of 'this.redirects[redirectId]' as it is undefined.`
This was caused by `redirectIds` that contained the same id multiple times.
* Added a test for adding a redirect multiple times and removing it once
* Fixed adding same redirect multiple times throws an error on removal
refs https://github.com/TryGhost/Team/issues/1091
The Offers feature needs to be able to add and remove redirects to Ghost
- which is very similar to the custom redirects functionality. Here we've
pulled out the core of the dynamic redirect part of custom redirects so
that it can be used by both features and have code shared between them.
