Atte Isopuro

Results 8 issues of Atte Isopuro

Rebased version of #928 All credit to @airlessproject for the commits.

This builds on the stale PR previously opened for this: #2180

The most notable change to the functionality is the way procurements avoid merging to existing purchases and purchase lines. I recommend reviewers pay particular attention to those parts of the...

## Depends on * #614 ## Notes * Includes an additional `[IMP]` commit since it wasn't strictly related to the migration. It can be squashed if the maintainers feel it...

Replaces (resurrects?) #626

Depends on: * #644 Built on top of the dependent PR, only the last commit is actually different.