Create repository with old versions of MariaDB Galera Cluster

I think it would be prudent to have a repository that contained older versions of MariaDB Galera Cluster, and not just the very latest version.

This is quite a complicated beast to install, as outlined by my request to update the documentation here:

https://mariadb.atlassian.net/browse/MDEV-6639
https://mariadb.com/kb/en/mariadb/documentation/getting-started/mariadb-binary-packages/installing-mariadb-deb-files/

For instance, if one wants to install MariaDB Galera Cluster 5.5.38 (5.5.39 is the current latest), then one must jump through many hoops, and know many other details, in order to successfully pull this off, at the moment.

For instance, the recommended way to install MariaDB Galera Cluster is:

apt-get install mariadb-galera-server

In fact, the docs even say (above link), that one shouldn't even try to install them in the manual way - but not everyone can run the latest and greatest:

"While it is not recommended, it is possible to download and install the packages manually (i.e. without a package manager like apt-get)."

Thus given that, and given the complexity of installing it manually, even when the documentation is cleared up, it would be much easier/safer to run something like (per apt-get man page info):

apt-get install mariadb-galera-server=5.5.38

But, for this to work, the older packages must be available. Hence this request.

Perhaps we could even have our own for just this case.