bolt_client support for the [bb8] connection pool.

Example

use std::env;

use bb8_bolt::{
    bb8::Pool,
    bolt_client::Metadata,
    bolt_proto::{version::*, Value},
    Manager,
};

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    // Configure a connection manager. We'll request Bolt v4.4 or v4.3.
    let manager = Manager::new(
        env::var("BOLT_TEST_ADDR")?,
        env::var("BOLT_TEST_DOMAIN").ok(),
        [V4_4, V4_3, 0, 0],
        Metadata::from_iter(vec![
            ("user_agent", "bolt-client/X.Y.Z"),
            ("scheme", "basic"),
            ("principal", &env::var("BOLT_TEST_USERNAME")?),
            ("credentials", &env::var("BOLT_TEST_PASSWORD")?),
        ]),
    ).await?;

    // Create a connection pool. This should be shared across your application.
    let pool = Pool::builder().build(manager).await?;

    // Fetch and use a connection from the pool
    let mut conn = pool.get().await?;
    let response = conn.run("RETURN 1 as num;", None, None).await?;
    let pull_meta = Metadata::from_iter(vec![("n", 1)]);
    let (records, response) = conn.pull(Some(pull_meta)).await?;
    assert_eq!(records[0].fields(), &[Value::from(1)]);

    Ok(())
}