Function create_invitation 

pub async fn create_invitation(
    storage: &dyn SyncStorage,
    cloud_home: &dyn CloudHome,
    chain: &mut MembershipChain,
    owner_keypair: &UserKeypair,
    invitee_ed25519_pubkey: &str,
    role: MemberRole,
    encryption_key: &[u8; 32],
    timestamp: &str,
) -> Result<CloudHomeJoinInfo, InviteError>

Create an invitation for a new member.

This grants access on the cloud home, wraps the library encryption key to the invitee’s X25519 public key, creates and signs a membership entry (Add), validates it against the local chain, and uploads both to the storage. Returns the JoinInfo so the caller can share connection details with the invitee.