Think about how to inform the user about changes in the mapping

[DedAnton]

Let's say the user updated the version of the library, the new version has some kind of bug due to which the user's old mappings stopped working correctly. But he will not know about it, because he is unlikely to check the code of all old mappings. Therefore, a mechanism is needed that will inform him that some changes have taken place.

I like the idea of storing the mapper code somewhere in the project folders so that it gets into the version control system, then when the user commits, the changes will be noticed. Or you can make the system as in testing with snapshots, so that the user is thrown into a diff with some changes, and he had to confirm them. But I think it's overkill in this case.