code: public static String buildMdmPayload(final String pushMagicValue) {
          return GSON.toJson(java.util.Collections.singletonMap(MDM_KEY, pushMagicValue));
      }
docs: Returns a JSON representation of a
  <a href="https://developer.apple.com/library/content/documentation/Miscellaneous/Reference/MobileDeviceManagementProtocolRef/1-Introduction/Introduction.html#//apple_ref/doc/uid/TP40017387-CH1-SW1">Mobile
  Device Management</a> "wake up" payload.
  
  @param pushMagicValue the "push magic" string that the device sends to the MDM server in a {@code TokenUpdate}
  message
  
  @return a JSON representation of an MDM "wake up" notification payload
  
  @see <a href="https://developer.apple.com/library/content/documentation/Miscellaneous/Reference/MobileDeviceManagementProtocolRef/3-MDM_Protocol/MDM_Protocol.html#//apple_ref/doc/uid/TP40017387-CH3-SW2">Mobile
  Device Management (MDM) Protocol</a>
  
  @since 0.12