See merge request !423

See merge request !429

   Events are creates via script (and API) now, instead jio_post.

Add `README.md` instructions explaining how to adapt the migration
tests after upgrading the proxy database version.

When migrating entries, use `INSERT OR REPLACE` to get rid of duplicate
rows that cause constraint violations, instead of raising an exception.

Note that this only affects the `forwarded_partition_request` table:
for other tables it changes nothing in terms of behavior because the
intial tables already cannot contain conflicting rows.

Insert duplicate entries in `forwarded_partition_request` table of each
database dump of previous versions, and assert that only a single entry
remains after the migration.

See merge request !427

See merge request !426

These scripts were re-implementing the download logic of download_playbook
with the difference being using a different name for the temporary file,
but we don't care about the temporary file name

Another difference was to edit slapcache.cfg once it is downloaded,
this part, we need to keep it.

Avoid bloating the proxy database due to each instance processing
adding the same entries for forwarded requests as duplicate rows
again and again, leading to unbounded growth.

See merge request !425