docs: fix README for influxdb_iox_client (#4825)

Closes #4816

influxdb_iox_client/README.md

@@ -2,61 +2,36 @@
 
 This is the official Rust client library for connecting to InfluxDB IOx.
 
-## Using the HTTP API
+Currently only gRPC is supported.
 
-If you only want to use the HTTP API, create an `influxdb_iox_client::Client`. Here is an example of
-creating an instance that connects to an IOx server running at `http://127.0.0.1:8080` and creating
-a database named `telemetry`:
+## Using the gRPC Write Client
+
+To write to IOx, create a connection and a write client, and then send line
+protocol. Here is an example of creating an instance that connects to an IOx
+server running at `http://127.0.0.1:8081` (the default bind address for the
+gRPC endpoint of IOx when running in all-in-one mode) and sending a line of
+line protocol:
 
 ```rust
 #[tokio::main]
 fn main() {
-    use data_types::database_rules::DatabaseRules;
-    use influxdb_iox_client::ClientBuilder;
+    use influxdb_iox_client::{
+        write::Client,
+        connection::Builder,
+    };
 
-    let client = ClientBuilder::default()
-        .build("http://127.0.0.1:8080")
-        .expect("client should be valid");
-
-    client
-        .create_database("telemetry", &DatabaseRules::default())
+    let mut connection = Builder::default()
+        .build("http://127.0.0.1:8081")
         .await
-        .expect("failed to create database");
-}
-```
+        .unwrap();
 
-## Using the Arrow Flight API
+    let mut client = Client::new(connection);
 
-IOx supports an [Arrow Flight gRPC API](https://arrow.apache.org/docs/format/Flight.html). To use
-it, enable the `flight` feature, which is off by default:
-
-```toml
-[dependencies]
-influxdb_iox_client = { version = "[..]", features = ["flight"] }
-```
-
-Then you can create an `influxdb_iox_client::FlightClient` by using the `FlightClientBuilder`. Here
-is an example of creating an instance that connects to an IOx server with its gRPC services
-available at `http://localhost:8082` and using it to perform a query:
-
-```rust
-#[tokio::main]
-fn main() {
-    use data_types::database_rules::DatabaseRules;
-    use influxdb_iox_client::FlightClientBuilder;
-
-    let client = FlightClientBuilder::default()
-        .build("http://127.0.0.1:8082")
-        .expect("client should be valid");
-
-    let mut query_results = client
-        .perform_query(scenario.database_name(), sql_query)
-        .await;
-
-    let mut batches = vec![];
-
-    while let Some(data) = query_results.next().await {
-        batches.push(data);
+    // write a line of line procol data
+    client
+        .write_lp("bananas", "cpu,region=west user=23.2 100",0)
+        .await
+        .expect("failed to write to IOx");
     }
 }
 ```

influxdb_iox_client/src/client/write.rs

@@ -29,7 +29,7 @@ use crate::error::Error;
 /// client
 ///     .write_lp("bananas", "cpu,region=west user=23.2 100",0)
 ///     .await
-///     .expect("failed to create database");
+///     .expect("failed to write to IOx");
 /// # }
 /// ```
 #[derive(Debug, Clone)]