I was working on fixing the CI errors (some of which are due to the TS-2150)
commit. During this I discovered that we have internally a milestone
UA_FIRST_READ that is not in the TSMilestonesType enum in apidefs.h. I think it
should be added but if it is added in the appropriate location this will be an
incompatible change, which would then have to be backported to 6.0. Fixing the
current build errors depends on this so I need a decision before I can complete
the fix. I think the best thing is to do a seperate bug/commit just for
UA_FIRST_READ and then I can depend on that on master to do the TS-2150 fixes.
