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/get-started.html

@@ -14,7 +14,7 @@
 <ol class="get-started-list">
   <li class="get-started-list__item">
     <h2 class="get-started-list__heading">Check if GOV.UK Notify is right for you</h2>
-    <p>Read about our <a href="{{ url_for('main.features') }}">features</a>, <a href="{{ url_for('.pricing') }}">pricing</a> and <a href="{{ url_for('main.roadmap') }}">roadmap</a>.</p>
+    <p>Read about our <a class="govuk-link govuk-link--no-visited-state" href="{{ url_for('main.features') }}">features</a>, <a class="govuk-link govuk-link--no-visited-state" href="{{ url_for('.pricing') }}">pricing</a> and <a class="govuk-link govuk-link--no-visited-state" href="{{ url_for('main.roadmap') }}">roadmap</a>.</p>
     {{ govukDetails({
       "summaryText": "Organisations that can use Notify",
       "html": '''
@@ -35,15 +35,15 @@
   <li class="get-started-list__item">
     <h2 class="get-started-list__heading">Create an account</h2>
     {% if not current_user.is_authenticated %}
-      <p><a href="{{ url_for('.register') }}">Create an account</a> for free and add your first Notify service. When you add a new service it will start in <a href="{{ url_for('main.trial_mode_new') }}">trial mode</a>.</p>
+      <p><a class="govuk-link govuk-link--no-visited-state" href="{{ url_for('.register') }}">Create an account</a> for free and add your first Notify service. When you add a new service it will start in <a class="govuk-link govuk-link--no-visited-state" href="{{ url_for('main.trial_mode_new') }}">trial mode</a>.</p>
     {% else %}
-      <p>Create an account for free and add your first Notify service. When you add a new service, it will start in <a href="{{ url_for('main.trial_mode_new') }}">trial mode</a>.</p>
+      <p>Create an account for free and add your first Notify service. When you add a new service, it will start in <a class="govuk-link govuk-link--no-visited-state" href="{{ url_for('main.trial_mode_new') }}">trial mode</a>.</p>
     {% endif %}
   </li>
 
   <li class="get-started-list__item">
     <h2 class="get-started-list__heading">Write some messages</h2>
-    <p>Add message templates with examples of the content you plan to send. You can use our <a href="{{ url_for('main.guidance_index') }}">guidance</a> to help you.</p>
+    <p>Add message templates with examples of the content you plan to send. You can use our <a class="govuk-link govuk-link--no-visited-state" href="{{ url_for('main.guidance_index') }}">guidance</a> to help you.</p>
   </li>
 
   <li class="get-started-list__item">
@@ -52,15 +52,15 @@
     <p>Review your settings to add message branding, reply-to addresses and sender information.</p>
     <p>Add team members and check their permissions.</p>
     {% else %}
-    <p>Review your <a href="{{ url_for('.service_settings', service_id=current_service.id) }}">settings</a> to add message branding, reply-to addresses and sender information.</p>
-    <p>Add <a href="{{ url_for('.manage_users', service_id=current_service.id) }}">team members</a> and check their permissions.</p>
+    <p>Review your <a class="govuk-link govuk-link--no-visited-state" href="{{ url_for('.service_settings', service_id=current_service.id) }}">settings</a> to add message branding, reply-to addresses and sender information.</p>
+    <p>Add <a class="govuk-link govuk-link--no-visited-state" href="{{ url_for('.manage_users', service_id=current_service.id) }}">team members</a> and check their permissions.</p>
     {% endif %}
   </li>
 
   <li class="get-started-list__item">
     <h2 class="get-started-list__heading">Set up an API integration (optional)</h2>
     <p>You can use the Notify API to send messages automatically.</p>
-    <p>Our <a href="{{ url_for('main.documentation') }}">documentation</a> explains how to integrate the API with a web application or back office system.</p>
+    <p>Our <a class="govuk-link govuk-link--no-visited-state" href="{{ url_for('main.documentation') }}">documentation</a> explains how to integrate the API with a web application or back office system.</p>
   </li>
 
   <li class="get-started-list__item">
@@ -68,9 +68,9 @@
     {% if not current_user.is_authenticated or not current_service %}
     <p>When you’re ready to send messages to people outside your team, go to the <b class="govuk-!-font-weight-bold">Settings</b> page and select <b class="govuk-!-font-weight-bold">Request to go live</b>. We’ll approve your request within one working day.</p>
     {% else %}
-    <p>You should <a href="{{ url_for('.request_to_go_live', service_id=current_service.id) }}">request to go live</a> when you’re ready to send messages to people outside your team. We’ll approve your request within one working day.</p>
+    <p>You should <a class="govuk-link govuk-link--no-visited-state" href="{{ url_for('.request_to_go_live', service_id=current_service.id) }}">request to go live</a> when you’re ready to send messages to people outside your team. We’ll approve your request within one working day.</p>
     {% endif %}
-    <p>Check <a href="{{ url_for('main.how_to_pay') }}">how to pay</a> if you’re planning to send letters or exceed the <a href="{{ url_for('.pricing', _anchor='text-messages') }}">free text message allowance</a>.</p>
+    <p>Check <a class="govuk-link govuk-link--no-visited-state" href="{{ url_for('main.how_to_pay') }}">how to pay</a> if you’re planning to send letters or exceed the <a class="govuk-link govuk-link--no-visited-state" href="{{ url_for('.pricing', _anchor='text-messages') }}">free text message allowance</a>.</p>
   </li>
 
 </ol>