[Placeholder from PMC] Consider enabling "contrib" modules that don't burden core PBS repo

[scr-oath]

At the moment every adapter, module, analytics, MetricsEngine is compiled into the core repo. This means that any of the existing or newly added options burdens the main repo with its dependencies.

The proposal would be to have a separate repo for contrib where each contribution could have its own go.mod/sum to declare its own dependencies. Then, hosting companies, could pick and choose which pieces they wanted and configure into the system rather than needing everything always even if not used.