Grants a customer viewer or editor access to an audience by their email.

Granting editor access implies viewing, and lets the recipient manage the audience — including starting recruiting and rebuilding the distilling campaign, which spend the owner's budget. Re-sharing at the same level is idempotent. An email with no matching account is accepted and grants nothing; the response does not distinguish it from a successful share, so callers cannot probe which emails have accounts. Sharing a filtered audience records the share against its base audience, which covers the base and every filtered audience derived from it.