Update all links to use GOVUK Frontend style

Includes:
- turning off :visited styles to match existing
  design
- swapping heading classes used to make links bold
  for the GOVUK Frontend bold override class
- adding visually hidden text to some links to
  make them work when isolated from their context

We may need to revisit whether some links, such as
those for documentation and features, may benefit
from having some indication that their target has
been visited.

app/templates/views/features.html

@@ -12,13 +12,13 @@
 <p>If you work for central government, a local authority or the NHS, you can use GOV.UK Notify to keep your users updated.</p>
 <p>Notify makes it easy to create, customise and send:</p>
 <ul class="list list-bullet">
-  <li><a href="{{ url_for('main.features_email') }}">emails</a></li>
-  <li><a href="{{ url_for('main.features_sms') }}">text messages</a></li>
-  <li><a href="{{ url_for('main.features_letters') }}">letters</a></li>
+  <li><a class="govuk-link govuk-link--no-visited-state" href="{{ url_for('main.features_email') }}">emails</a></li>
+  <li><a class="govuk-link govuk-link--no-visited-state" href="{{ url_for('main.features_sms') }}">text messages</a></li>
+  <li><a class="govuk-link govuk-link--no-visited-state" href="{{ url_for('main.features_letters') }}">letters</a></li>
 </ul>
 <p>You do not need any technical knowledge to use Notify.</p>
 {% if not current_user.is_authenticated %}
-  <p><a href="{{ url_for('main.register') }}">Create an account</a> for free and try it yourself.</p>
+  <p><a class="govuk-link govuk-link--no-visited-state" href="{{ url_for('main.register') }}">Create an account</a> for free and try it yourself.</p>
 {% endif %}
 
 <h2 class="heading-medium" id="templates">Reusable message templates</h2>
@@ -34,11 +34,11 @@
 
 <h2 class="heading-medium" id="api">API integration</h2>
 <p>You can integrate the Notify API with your web application or back-office system to send messages automatically.</p>
-<p>Read our <a href="{{ url_for('.documentation') }}">API documentation</a> for more information.</p>
+<p>Read our <a class="govuk-link govuk-link--no-visited-state" href="{{ url_for('.documentation') }}">API documentation</a> for more information.</p>
 
 <h2 class="heading-medium" id="reporting">Reporting</h2>
 <p>Notify’s real-time dashboard lets you see the number of messages sent. You can also check the current status of any message to see when it was delivered.</p>
-<p>Read more about the <a href="{{ url_for('main.message_status') }}">delivery status</a> of your messages.</p>
+<p>Read more about the <a class="govuk-link govuk-link--no-visited-state" href="{{ url_for('main.message_status') }}">delivery status</a> of your messages.</p>
 
 <h2 class="heading-medium" id="permissions">Permissions</h2>
 <p>Control which members of your team can see, create, edit and send messages.</p>
@@ -58,7 +58,7 @@
 
 <p>We send messages through several different providers. If one provider fails, Notify switches to another so that your messages are not affected.</p>
 
-<p>Visit GOV.UK Performance to <a href="https://www.gov.uk/performance/govuk-notify">see how Notify is performing</a>.</p>
+<p>Visit GOV.UK Performance to <a class="govuk-link govuk-link--no-visited-state" href="https://www.gov.uk/performance/govuk-notify">see how Notify is performing</a>.</p>
 
 <h2 class="heading-medium" id="security">Security</h2>
 <p>Notify protects and manages data to meet the needs of government services.</p>
@@ -68,10 +68,10 @@
 
 <h3 class="heading-small">Two-factor authentication</h3>
 <p>Notify uses two-factor authentication (2FA) to keep your account secure. When you sign in, we’ll send a unique one-time code to your phone and ask you to enter it before we let you use your account.</p>
-<p>Read more about <a href="{{ url_for('main.security') }}">security</a>.
+<p>Read more about <a class="govuk-link govuk-link--no-visited-state" href="{{ url_for('main.security') }}">security</a>.
 
 <h2 class="heading-medium" id="support">Support</h2>
 <p>Notify provides 24-hour online support. If you have an emergency outside office hours, we’ll reply within 30 minutes.</p>
-<p>Find out more about <a href="{{ url_for('.support') }}">support</a>.</p>
+<p>Find out more about <a class="govuk-link govuk-link--no-visited-state" href="{{ url_for('.support') }}">support</a>.</p>
 
 {% endblock %}