Milestone-release - have many-to-many relationship
Problem to solve
I'd like to start a conversation about that MVC strategy applied to the milestone-release issue.
It was decided to have a MVC for the new milestone-release relationship, creating a one-to-one relationship. Post-MVC, we would go towards a many-to-many relationship. By having adopted this strategy, I'm now seeing a red flag as I believe more and more that we should have gone towards a many-to-many relationship right away.
Having an MVC will end up duplicating effort on subsequent issues. For example, the scope of this issue will differ whether we deal with a milestone-release MVC or post-MVC. At some point, once we establish a many-to-many relationship, I'm afraid that many 12.4 issues (and other later issues?) will have to be updated accordingly.
From an Agile point-of-view, I think an MVC makes sense if it does not create "externalities". Said differently, I'm happy to iterate on that feature a few times but it should not be to the detriment of many other related features (and their scope).
Finally (but I may not be 100% correct here), I believe UX and front-end are already working with having "many-to-many" relationship. cc @nfriend @rverissimo
Proposal
The milestone-release BE work was merged yesterday morning. So this MR here is really about addressing the merged one-to-one relationship (Rails-level only) and to fully make it many-to-many.