Document and release 1.30.4-1pureos1 into octarine

Marked as draft, because I'm not 100% sure that I've fixed the upstream/latest and pristine-tar branch which have diverged from upstream Debian.

For the pureos/byzantium branch I used gbp import-ref, then git merge debian/1.30.4-1. On the upstream/latest (pushed as test-upstream/latest) I git merge salsa/upstream/latest -X theirs and then git diff | git apply and then git commit --amend.

On the pristine-tar branch (pushed as test-pristine-tar) I just git merge salsa/pristine-tar. git diff | git apply did not want to apply and so a diff remains. However I've made sure that the checksums of the tarballs exported from salsa/pristine-tar test-pristine-tar match, so I don't think this should be a problem (?)

I would appreciate if someone can have another look at the work with respect to it being fast-forwardeable from salsa for the next releases :)

If everything is fine I can push pristine-tar and upstream/latest with the correct names.