Connect to systemd over session DBus rather than system (#2)

This seems to be correct for starting user services.

Cargo.lock

@@ -251,6 +251,7 @@ dependencies = [
  "tracing",
  "tracing-journald",
  "tracing-subscriber",
+ "zbus",
 ]
 
 [[package]]

Cargo.toml

@@ -23,3 +23,4 @@ tokio-util = "0.7"
 tracing = "0.1"
 tracing-journald = "0.3.0"
 tracing-subscriber = { version = "0.3", features = ["env-filter"] }
+zbus = { version = "2.0.1" }

src/systemd.rs

@@ -1,9 +1,11 @@
 // SPDX-License-Identifier: GPL-3.0-only
 
 use color_eyre::{eyre::WrapErr, Result};
+use systemd_client::manager::SystemdManagerProxy;
 
 pub async fn start_systemd_target() -> Result<()> {
-	let manager = systemd_client::manager::build_nonblock_proxy()
+	let connection = zbus::Connection::session().await?;
+	let manager = SystemdManagerProxy::new(&connection)
 		.await
 		.wrap_err("failed to connect to org.freedesktop.systemd1.Manager")?;
 	manager