Batch alias transfer

Problem

Currently, SimpleLogin only supports transferring aliases individually. Migrating all or many aliases to a new SimpleLogin account is very tedious. The process is also slowed down by the apparent rate limiting of the existing feature: the user receives a 429 error page after transferring 2–3 aliases within a short period of time.

The existing import/export feature is only supported for custom domains, so this does not address this use case when the aliases are non-custom domains.

Suggested feature

Support transferring all or multiple aliases.