### PKI storage migration revives deleted issuers

Vault 1.11 introduced Storage v1, a new storage layout that supported
multiple issuers within a single mount. Bug fixes in Vault 1.11.6, 1.12.2,
and 1.13.0 corrected a write-ordering issue that lead to invalid CA chains.
Specifically, incorrectly ordered writes could fail due to load, resulting
in the mount being re-migrated next time it was loaded or silently
truncating CA chains. This collection of bug fixes introduced Storage v2.

#### Affected versions

Vault may incorrectly re-migrated legacy issuers created before Vault 1.11 that
were migrated to Storage v1 and deleted before upgrading to a Vault version with
Storage v2.

The migration fails when Vault finds managed keys associated with the legacy
issuers that were removed from the managed key repository prior to the upgrade.

The migration error appears in Vault logs as:

> Error during migration of PKI mount:
>   failed to lookup public key from managed key:
>     no managed key found with uuid

<Note>
Issuers created in Vault 1.11+ and direct upgrades to a Storage v2 layout are
not affected.
</Note>

The Storage v1 upgrade bug was fixed in Vault 1.14.1, 1.13.5, and 1.12.9.
