feat: add debug server for tailnet coordinators (#5861)

Implements a Tailscale-like debug server for our in-memory coordinator. This should provide some visibility into why connections could be failing.
Resolves: https://github.com/coder/coder/issues/5845

![image](https://user-images.githubusercontent.com/6332295/214680832-2724d633-2d54-44d6-a7ce-5841e5824ee5.png)

coderd/workspaceagents.go

@@ -521,6 +521,16 @@ func (api *API) workspaceAgentCoordinate(rw http.ResponseWriter, r *http.Request
 		})
 		return
 	}
+
+	workspace, err := api.Database.GetWorkspaceByID(ctx, build.WorkspaceID)
+	if err != nil {
+		httpapi.Write(ctx, rw, http.StatusBadRequest, codersdk.Response{
+			Message: "Internal error fetching workspace.",
+			Detail:  err.Error(),
+		})
+		return
+	}
+
 	// Ensure the resource is still valid!
 	// We only accept agents for resources on the latest build.
 	ensureLatestBuild := func() error {
@@ -618,7 +628,7 @@ func (api *API) workspaceAgentCoordinate(rw http.ResponseWriter, r *http.Request
 	closeChan := make(chan struct{})
 	go func() {
 		defer close(closeChan)
-		err := (*api.TailnetCoordinator.Load()).ServeAgent(wsNetConn, workspaceAgent.ID)
+		err := (*api.TailnetCoordinator.Load()).ServeAgent(wsNetConn, workspaceAgent.ID, fmt.Sprintf("%s-%s", workspace.Name, workspaceAgent.Name))
 		if err != nil {
 			api.Logger.Warn(ctx, "tailnet coordinator agent error", slog.Error(err))
 			_ = conn.Close(websocket.StatusInternalError, err.Error())