Answers whether a card program already has an open bulk enrollment kickoff, before anyone
fills in the kickoff form. The Unified Enrollment SDK calls it while it looks up a card, and
shows "Already under way" instead of the program screen when the program has one; you can
also call it directly.

A program is the calling account, the subaccountId, the network and the card's first 8
digits (bin). The rule is the one POST /network-bulk-enrollments uses: a kickoff is open
while it is requested and was created less than 90 days ago, or while it is feed-created
and its feed is live, at any age. The account comes from the token, never from the query.

The answer carries only the open kickoff's enrollmentId, state and requestedAt. A
bin of more or fewer than 8 digits, a missing or unknown parameter, or an accountId in
the query answers 400.

Requires the network-bulk-enrollments:write scope, the one the kickoff itself takes.
Tokens that only hold network-bulk-feeds:write are also accepted. A token with only a read
scope answers 403.