ADMIN

Lists a campaign's batches, newest first. This is how a drop is found
again: batch_id is otherwise only ever returned in the 202 that
created the batch, and it is what withdrawing a batch requires.

campaign_id is required — the index is keyed by campaign.

Passing tag resolves the single batch holding that tag, which is the
handle an operator is likely to have. Tags are unique per campaign, so
the result is at most one batch; a withdrawal reuses its target's tag, so
a tag that has been withdrawn returns the original batch, not the
deletion. Batches created before tagging existed are not reachable this
way and neither are vouchers imported through the CLI without -tag,
which have no batch record at all.