Populate the user data of worktree collaborators

This will make it possible for us to render their avatars. Previously we only had the user ids. During rendering, everything needs to be available synchronously. So now, whenever collaborators are added, we perform the async I/O to fetch their user data prior to adding them to the worktree.

crates/client/src/test.rs

@@ -2,7 +2,7 @@ use super::Client;
 use super::*;
 use crate::http::{HttpClient, Request, Response, ServerResponse};
 use futures::{future::BoxFuture, Future};
-use gpui::TestAppContext;
+use gpui::{ModelHandle, TestAppContext};
 use parking_lot::Mutex;
 use postage::{mpsc, prelude::Stream};
 use rpc::{proto, ConnectionId, Peer, Receipt, TypedEnvelope};
@@ -155,6 +155,24 @@ impl FakeServer {
     fn connection_id(&self) -> ConnectionId {
         self.connection_id.lock().expect("not connected")
     }
+
+    pub async fn build_user_store(
+        &self,
+        client: Arc<Client>,
+        cx: &mut TestAppContext,
+    ) -> ModelHandle<UserStore> {
+        let http_client = FakeHttpClient::with_404_response();
+        let user_store = cx.add_model(|cx| UserStore::new(client, http_client, cx));
+        assert_eq!(
+            self.receive::<proto::GetUsers>()
+                .await
+                .unwrap()
+                .payload
+                .user_ids,
+            &[self.user_id]
+        );
+        user_store
+    }
 }
 
 pub struct FakeHttpClient {