Many of our changes will be safe to deploy immediately, and will handle legacy maps traffic.
Do not merge anything until we have the full migration planned, see T293843.
Make sure all patches that go to master have tests added, if possible.
* [] mapdata repo
* [] {T293334}
* [] Merge our branch to master
* [] Kartographer
* [] {T294732}
* [] Merge our branch to master
* [] Kartotherian
* [] Cover legacy mapdata pass-through
* [] Cover revid pass-through with tests
* [] Test feature flag for killing revid pass-through
* [] Merge our branch to master
* [] varnish
* [] Write varnishtest to cover the hash calculation
* [] Test that revid URLs hash to the same as a legacy URL without revid.
* [] Test that revid regsub cannot be fooled by parameter order, invalid, or missing values