Consider single code-base template, building multiple charms

Look at how we do it in https://github.com/canonical/template-connect-integrator

There is a common core 'charm', but each implementation of different connectors (in this case, cloud storages), have their own config and minor tweaks.

Makes it more maintainable

Start by reviewing the existing object-storage-integrator code and the linked template-connect-integrator repository. Compare how the common charm core, connector-specific configuration, and minor implementation differences are organized. Done would mean a maintainable shared code base supporting the different connectors, but the issue does not name files or provide concrete acceptance criteria.

Written by the indexing model from the issue text.