The admin set-admin-flag, set-status and delete-user operations were
implemented twice — once in the v1 echo handlers, once in the v2 Huma handlers.
Extract the load/guard/mutate logic into models.SetUserAdminFlag,
models.SetUserStatusAsAdmin and models.DeleteUserAsAdmin so both APIs call the
same code; each handler keeps only its own request binding, validation and
response shape. v1 stays byte-identical on the wire.
kolaente