[debian-mysql] Heads up to release team about MariadB 10.3

[Otto Kekäläinen]

Hello!

I just realized that the upload of mariadb-10.3 into Debian includes
the following transitions:
- libmariadbd18 -> libmariadbd19
- libmariadbclient18 becomes deprecated and fully replaced by the
libmariadb3 library already in Debian for a longer time (source
package mariadb-connector-c)

Technically this can constitute a transition and I have not followed
the process desrcibed at:
https://wiki.debian.org/Teams/ReleaseTeam/Transitions

My priority has been in packaging mariadb-10.3 so we would not be
stuck with mariadb-10.1 in buster. It is a very large package and this
transition was just a smal part of it, and I realized it too late.

My focus was mostly on if I manage to pull this off at all in time,
and I overlooked planning this transition detail. Sorry!

Luckily there has not been any major problems so far. The Salsa-CI,
ci.debian.net etc are all looking good. There is maybe just one issue
that can be hard to tackle, details in
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=917303