Function add_chat_member 

pub async fn add_chat_member(
    chat_id: i64,
    user_id: i64,
    forward_limit: i32,
    client_id: i32,
) -> Result<FailedToAddMembers, Error>

Adds a new member to a chat; requires can_invite_users member right. Members can’t be added to private or secret chats. Returns information about members that weren’t added

Arguments

• chat_id - Chat identifier
• user_id - Identifier of the user
• forward_limit - The number of earlier messages from the chat to be forwarded to the new member; up to 100. Ignored for supergroups and channels, or if the added user is a bot
• client_id - The client id to send the request to