code: public OvhVolume project_serviceName_volume_volumeId_upsize_POST(String serviceName, String volumeId, Long size) throws IOException {
  		String qPath = "/cloud/project/{serviceName}/volume/{volumeId}/upsize";
  		StringBuilder sb = path(qPath, serviceName, volumeId);
  		HashMap<String, Object>o = new HashMap<String, Object>();
  		addBody(o, "size", size);
  		String resp = exec(qPath, "POST", sb.toString(), o);
  		return convertTo(resp, OvhVolume.class);
  	}
docs: Extend a volume
  
  REST: POST /cloud/project/{serviceName}/volume/{volumeId}/upsize
  @param serviceName [required] Service name
  @param size [required] New volume size (in GiB) (must be greater than current one)
  @param volumeId [required] Volume id