allow agents to switch environments

see https://gitlab.torproject.org/tpo/tpa/puppet-hiera-enc/-/merge_requests/1

changed milestone to %Puppet CI

added Next Puppet lifecycle labels

assigned to @lavamind

added Needs Review label and removed Next label

for the record, in #41994 (closed) i actually went in the ENC checkout and changed environments with vi instead of doing commits and push because that's easier. :p

added Doing label and removed Needs Review label

mentioned in issue #42004 (closed)

marked this issue as related to #42004 (closed)

i think the last step here is to document the "be careful with environments" thing

i redid a MR here to make sure we don't lose track of that patch, which was deleted by a bad hook in the past. i changed it slightly to also update the README file.

mentioned in commit wiki-replica@166f3436

this was done in puppet-hiera-enc!2

closed