fix: Make the influx client data_point module public

Driven by use in fusion.

influxdb2_client/src/data_point.rs

@@ -1,3 +1,5 @@
+//! Data point building and writing
+
 use snafu::{ensure, Snafu};
 use std::{collections::BTreeMap, io};
 

influxdb2_client/src/lib.rs

@@ -60,7 +60,7 @@ use reqwest::Body;
 use snafu::{ResultExt, Snafu};
 use std::io::{self, Write};
 
-mod data_point;
+pub mod data_point;
 pub use data_point::{DataPoint, FieldValue, WriteDataPoint};
 
 /// Errors that occur while making requests to the Influx server.