Consider merging publishing pipeline repositories

This is to do with our external repositories. We'd like to consider whether we can merge them together to make them easier to work with.

Start by identifying the external publishing pipeline repositories referred to in the issue and documenting how each is used. Compare their boundaries and workflows, then define whether merging them would make them easier to work with and record the resulting recommendation; no files or tests are named.

Written by the indexing model from the issue text.