PayPalOneTouch/src/main/java/com/paypal/android/sdk/onetouch/core/PayPalOneTouchCore.java
@MainThread
    public static String getClientMetadataId(Context context, String pairingId) {
        return PayPalDataCollector.getClientMetadataId(context, pairingId);
    }
@MainThread
    public static String getClientMetadataId(Context context, String pairingId) {
        return PayPalDataCollector.getClientMetadataId(context, pairingId);
    }
Gets a Client Metadata ID at the time of payment activity. Once a user initiates a PayPal payment
from their device, PayPal uses the Client Metadata ID to verify that the payment is
originating from a valid, user-consented device and application. This helps reduce fraud and
decrease declines. This method MUST be called prior to initiating a pre-consented payment (a
"future payment") from a mobile device. Pass the result to your server, to include in the
payment request sent to PayPal. Do not otherwise cache or store this value.

@param context The application context
@param pairingId The desired pairing id
@return clientMetadataId Your server will send this to PayPal