Because Django's ContentType objects are, by default, created lazily
when an actual object is created that will use them, this migration
would fail on any server that actually had RealmReactivationStatus
objects already, and had not yet created the ContentType for them.
ContentType objects are very simple:
zulip=> select * from django_content_type where model = 'realmreactivationstatus';
id | app_label | model
----+-----------+-------------------------
85 | zerver | realmreactivationstatus
So we can simply patch this by using get_or_create.
A user ran into an issue while upgrading where
ContentType.objects.get(model="realmreactivationstatus",
app_label="zerver") fails due to the object being missing. The reason
for that is to be yet figured out, but the immediate solution is clear
in the sense that the migration can just quit early
if not Confirmation.objects.filter(type=REALM_REACTIVATION).exists() and
that'll effectively skip it for almost all servers (because realm
reactivations links are something that's really only useful on Zulip
Cloud).