open grpc channel:
           - for http://  we open insecure_channel
           - for https:// we open secure_channel (with default credentials)
           - without prefix we open insecure_channel

def open_grpc_channel(endpoint):
    """
       open grpc channel:
           - for http://  we open insecure_channel
           - for https:// we open secure_channel (with default credentials)
           - without prefix we open insecure_channel
    """
    if (endpoint.startswith("https://")):
        return grpc.secure_channel(remove_http_https_prefix(endpoint), grpc.ssl_channel_credentials())
    return grpc.insecure_channel(remove_http_https_prefix(endpoint))