Function invite_member 

pub async fn invite_member(
    storage: &dyn SyncStorage,
    cloud_home: &dyn CloudHome,
    user_keypair: &UserKeypair,
    hlc: &Hlc,
    public_key_hex: &str,
    role: MemberRole,
    encryption_key: &[u8; 32],
    library_id: &str,
    library_name: &str,
) -> Result<InviteCode, MembershipOpsError>

Invite a member to the shared library.

Downloads the membership chain (bootstrapping a founder entry if needed), creates a signed Add entry, wraps the encryption key to the invitee’s public key, and uploads everything to the sync storage.

Returns the JoinInfo for building an invite code.