functions: Added function to enable custom module
As described in RQF2361514, a recent release of Ceph Quincy requires libarrow-devel and parquet-libs-devel, which express a dependency against utf8proc-devel. This latter is excluded by yum/dnf because of is filtered out by modular filtering
. Enabling module 'subversion-devel' allows pulling in utf8proc-devel.
Code is untested.