This thing sounds like it will depend on all of the same things that DataModelServices currently does!

The I feel the ideal situation (though maybe not the one we are going for here) would be to included the generation of summaries in DMServices. Diffs would be taken between 2 versions of an entity and then a summary be created from that diff. Though as I said previously this is more than T101836 is asking for.

If the scope of this (sub)component is "all the changes stuff", then DataModelServices does not seem like a viable location due to dependencies. There will be presentation things in there and need for stuff such as i18n. Presumably it'd also need to know about specific data values, which is something DMS does not.

If it needs i18n, would that component depend on MediaWiki? Would it be a standalone extension then? We haven't really figured out yet how to deal with possible subcomponents that need parts of MediaWiki.

It would be really nice to have all of the language stuff factored out of core and into a library.
I had a little chat with @Legoktm about it and apparently it would be very hard (even if I can see multiple uses of it for us here and in other parts of our code)

Indeed if this stuff needs to rely on mediawiki stuff then it should be somewhere else...

I have created a little component to wrap the MW i18n stuff for some extension where I wanted my code to not rely on global state and bind to MW. It's far from a full wrapper though, and I'm not convinced that creating a full one makes sense, which includes concerns about the difficulty of creation. Anyway, this might still be of interest:

https://github.com/JeroenDeDauw/i18n