Function new_identity 

pub async fn new_identity<ApiClient, S>(
    inbox_id: String,
    identifier: Identifier,
    nonce: u64,
    api_client: &ApiClientWrapper<ApiClient>,
    mls_storage: &S,
    scw_signature_verifier: impl SmartContractSignatureVerifier,
) -> Result<Identity, IdentityError>
where
    ApiClient: XmtpApi,
    S: XmtpMlsStorageProvider,

Create a new Identity instance.

If the address is already associated with an inbox_id, the existing inbox_id will be used. If it is not, a new inbox_id is generated from the identifier and nonce. Either way, the caller must sign with their wallet.