Fix postgres errors when running tests

test/support/conn_case.ex

@@ -123,7 +123,13 @@ defmodule MvWeb.ConnCase do
   end
 
   setup tags do
-    Mv.DataCase.setup_sandbox(tags)
-    {:ok, conn: Phoenix.ConnTest.build_conn()}
+    pid = Mv.DataCase.setup_sandbox(tags)
+
+    conn = Phoenix.ConnTest.build_conn()
+    # Set metadata for Phoenix.Ecto.SQL.Sandbox plug to allow LiveView processes
+    # to share the test's database connection in async tests
+    conn = Plug.Conn.put_private(conn, :ecto_sandbox, pid)
+
+    {:ok, conn: conn}
   end
 end