Pretix and Pretalx both use CalVer, so we don't want to have upgrades to
their second number be identified as minor updates and get grouped with
all the other minor and patch updates.
The regex to re-classify the second number as major doesn't work.
Probably because of:
"Important: all capture groups must contain only purely numeric values."
(https://docs.renovatebot.com/modules/versioning/regex/)
So instead match on the minor update type for Pretix and Pretalx and set
the group name to null.
The benefit of digest pinning isn't that great for this project really
and it comes at the cost of more issues and additional renovate noise,
so just don't anymore.
Adjust renovate config accordingly as well.
Since Forgejo seems to clean up older tag versions, so older digests,
disable digest pinning for our images.
While generally resulting in undeployable config, with ansible-pull the
breakage is especially noticeable.
Add custom package rule accounting for pretix calendar versioning to not
have Renovate classify month updates as minor version updates, but major
version updates instead.
