Function create_or_lookup_mailinglist_or_broadcast

async fn create_or_lookup_mailinglist_or_broadcast(
    context: &Context,
    allow_creation: bool,
    list_id_header: &str,
    from_id: ContactId,
    mime_parser: &MimeMessage,
) -> Result<Option<(ChatId, Blocked, bool)>>

Create or lookup a mailing list or incoming broadcast channel chat.

list_id_header contains the Id that must be used for the mailing list and has the form Name <Id>, <Id> or just Id. Depending on the mailing list type, list_id_header was picked from ListId:-header or the Sender:-header.

mime_parser is the corresponding message and is used to figure out the mailing list name from different header fields.

Returns the chat ID, whether it is blocked and if the chat was created by this function (as opposed to being looked up among existing chats).