While currently a recovery link is only made available via the admin email address, this will be expanded in the future. In order to accomplish that, the mechanisms to store and validate recovery keys must support multiple keys to be valid at the same time.
This changeset adds that support, adding an additional token parameter which is part of a recovery link in addition to the key. A key itself is always associated with a token, so the two are only valid in combination. These associations are stored in a new `recovery_keys` option, which is regularly cleared in a new Cron hook, to prevent potential cluttering from unused recovery keys.
This changeset does not have any user-facing implications otherwise.
Props pbearne, timothyblynjacobs.
Fixes#46595. See #46130.
git-svn-id: https://develop.svn.wordpress.org/trunk@45211 602fd350-edb4-49c9-b593-d223f7449a82
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