New game
<%= form_for @changeset, game_path(@conn, :create), [class: "create-game"],
fn form -> %>
<%= label form, :opponent_id %>
<%= select form, :opponent_id, @opponents, prompt: "Choose an opponent" %>
<%= error_tag form, :opponent_id %>
<%= submit "Create game", class: "button" %>
<% end %>