Which JNDI entry is used to configure a proxy for Google Cloud Messaging/Firebase Cloud Messaging?
A. mfp.push.proxy.*
B. mfp.push.wsn.proxy.*
C. mfp.push.gcm.proxy.*
D. mfp.push.apns.proxy.*
Reference: https://mobilefirstplatform.ibmcloud.com/blog/2015/09/10/configure-push-notification-proxy/