Make result summary available behind a feature flag

[knutwalker]

With this change it is possible to access to result summary of a query by enabling the unstable-v1 feature:

use neo4rs::*;
use neo4rs::summary::{Type, Counters, ResultSummary};

#[derive(Debug, PartialEq, serde::Deserialize)]
struct Person {
    name: String,
}

async fn example() -> Result<()> {
    let uri = "127.0.0.1:7687";
    let user = "neo4j";
    let pass = "password";
    let graph = Graph::new(uri, user, pass).await?;
    
    let mut stream = graph
        .execute(query("CREATE (n:Person {name: 'Alice'}) RETURN n"))
        .await?;

    let people = stream.into_stream_as::<Person>()
        .try_collect::<Vec<_>>()
        .await?;

    for person in people {
        assert_eq!(person.name, "Alice");
    }

    let Some(summary) = stream.finish().await? else { panic!("no summary available") };
    let summary: ResultSummary = summary; // The type of the summary

    assert!(summary.available_after().is_some());
    assert!(summary.consumed_after().is_some());
    assert!(summary.db().is_some());
    assert_eq!(summary.query_type(), Type::ReadWrite);
    assert_eq!(summary.stats(), &Counters {
        nodes_created: 1,
        properties_set: 1,
        labels_added: 1,
        ..Default::default()
    });
}

The API is behind an unstable feature flag, so it might change before it is available without a feature flag.

[jexp]

Nice 👍🏼