Function deltachat::receive_imf::create_or_lookup_group

async fn create_or_lookup_group(
    context: &Context,
    mime_parser: &mut MimeMessage,
    is_partial_download: bool,
    allow_creation: bool,
    create_blocked: Blocked,
    from_id: ContactId,
    to_ids: &[ContactId],
    verified_encryption: &VerifiedEncryption
) -> Result<Option<(ChatId, Blocked)>>

This function tries to extract the group-id from the message and returns the corresponding chat_id. If the chat does not exist, it is created. If there is no group-id and there are more than two members, a new ad hoc group is created.

On success the function returns the found/created (chat_id, chat_blocked) tuple.