Function deltachat::receive_imf::has_verified_encryption

async fn has_verified_encryption(
    context: &Context,
    mimeparser: &MimeMessage,
    from_id: ContactId,
    to_ids: &[ContactId]
) -> Result<VerifiedEncryption>

Checks whether the message is allowed to appear in a protected chat.

This means that it is encrypted and signed with a verified key.

Also propagates gossiped keys to verified if needed.