projekteuler/app/views/layouts/_header.html.erb

<nav class="navbar navbar-expand-lg navbar-light bg-light">
  <div class="container">
    <%= link_to t('application.site_title'), root_path, class: 'navbar-brand' %>
    <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarSupportedContent" aria-controls="navbarSupportedContent" aria-expanded="false" aria-label="Toggle navigation">
      <span class="navbar-toggler-icon">
        <%= icon('fas', 'bars') %>
      </span>
    </button>
    <div class="collapse navbar-collapse" id="navbarSupportedContent">
        <ul class="navbar-nav mr-auto">
            <%= nav_link_to t('application.info'), about_info_path %>
            <%= nav_link_to Problem.model_name.human(count: 2), problems_path %>
            <% if user_signed_in? and current_user.admin? %>
                <%= nav_link_to t('admin.dashboard.index.administration'), admin_dashboard_index_path %>
                <%= link_to admin_translations_path, class: 'nav-link' do %>
                  <%= t('admin.dashboard.index.translations') %> <span class="badge badge-secondary"><%= Translation.pending.count %></span>
                <% end %>
            <% end %>
        </ul>
        <ul class="navbar-nav">
          <% if user_signed_in? %>
            <li class="nav-item">
              <span class="navbar-text"><%= t 'application.logged_in_as_html', name: current_user.name %>
                <% if current_user.admin? %>
                  <b><%= icon('fas', 'star') %></b>
                <% end %>
              </span>
            </li>
            <li class="nav-item">
              <%= link_to t('application.sign_out'), destroy_user_session_path, method: :delete, class: 'nav-link' %>
            </li>
          <% else %>
            <li class="nav-item">
              <% if Rails.env.development? %>
                <%= link_to t('application.sign_in_with_github'), user_developer_omniauth_authorize_path, method: :post, class: 'nav-link' %>
              <% else %>
                <%= link_to t('application.sign_in_with_github'), user_github_omniauth_authorize_path, method: :post, class: 'nav-link' %>
              <% end %>
            </li>
          <% end %>
        </ul>
    </div>
  </div>
</nav>