Don’t allow paragraphs without class attribute

All paragraphs should have class="govuk-body", or be otherwise
custom-styled. This commit adds some extra checks to our test fixture
that looks for paragraphs that don’t have any styling. Our test coverage
is pretty good, so this should check almost all pages, and prevent
regressions.

I’ve done this in such a way that it can be extended for other elements
(e.g. links) in the future.

app/templates/views/agreement/agreement-confirm.html

@@ -20,11 +20,11 @@
     {% call form_wrapper(class='top-gutter') %}
 
       {% if current_service.organisation.agreement_signed_on_behalf_of_name and current_service.organisation.agreement_signed_on_behalf_of_email_address %}
-        <p>
+        <p class="govuk-body">
           I confirm that I have the legal authority to accept the GOV.UK Notify data sharing and financial agreement (version {{ current_service.organisation.agreement_signed_version }}) on behalf of {{ current_service.organisation.agreement_signed_on_behalf_of_name }} ({{ current_service.organisation.agreement_signed_on_behalf_of_email_address }}) and that {{ current_service.organisation.name }} will be bound by it.
         </p>
       {% else %}
-        <p>
+        <p class="govuk-body">
           I confirm that I have the legal authority to accept the GOV.UK Notify data sharing and financial agreement (version {{ current_service.organisation.agreement_signed_version }}) and that {{ current_service.organisation.name }} will be bound by it.
         </p>
       {% endif %}

app/templates/views/agreement/agreement-public.html

@@ -14,10 +14,10 @@
       Download the GOV.UK Notify data sharing and financial agreement
     </h1>
 
-    <p>
+    <p class="govuk-body">
       <a class="govuk-link govuk-link--no-visited-state" href="{{ download_link }}">Download the agreement</a>{% if owner %} for {{ owner }}{% endif %}.
     </p>
-    <p>
+    <p class="govuk-body">
       The agreement contains commercially sensitive information. Do not share it outside your organisation.
     </p>
 

app/templates/views/agreement/service-agreement-choose.html

@@ -15,19 +15,19 @@
       back_link=url_for('main.request_to_go_live', service_id=current_service.id)
     )}}
 
-    <p>
+    <p class="govuk-body">
       Before you can use GOV.UK Notify, you need to accept our data sharing and financial agreement.
     </p>
-    <p>
+    <p class="govuk-body">
       This must be done by, or on behalf of, someone with the authority to sign contracts for your organisation.
     </p>
-    <p>
+    <p class="govuk-body">
       Once accepted, the agreement covers all Notify services from your organisation.
     </p>
-    <p>
+    <p class="govuk-body">
       There are different agreements for crown and non-crown organisations.
     </p>
-    <p>
+    <p class="govuk-body">
       <a class="govuk-link govuk-link--no-visited-state" href="{{ url_for('main.support') }}">Contact us</a> to tell us
       whether or not you work for a crown organisation. If you’re not sure
       we’ll help you work it out.

app/templates/views/agreement/service-agreement-signed.html

@@ -15,13 +15,13 @@
       back_link=url_for('main.request_to_go_live', service_id=current_service.id)
     )}}
 
-    <p>
+    <p class="govuk-body">
       {{ current_service.organisation.name }} has already accepted the GOV.UK
       Notify data sharing and financial agreement.
     </p>
-    <p>For more information, you can <a class="govuk-link govuk-link--no-visited-state" href="{{ url_for('main.service_download_agreement', service_id=current_service.id) }}">download a copy of the agreement</a>.
+    <p class="govuk-body">For more information, you can <a class="govuk-link govuk-link--no-visited-state" href="{{ url_for('main.service_download_agreement', service_id=current_service.id) }}">download a copy of the agreement</a>.
     </p>
-    <p>
+    <p class="govuk-body">
       The agreement is confidential and should not be shared outside your organisation.
     </p>
 

app/templates/views/agreement/service-agreement.html

@@ -16,19 +16,19 @@
       back_link=url_for('main.request_to_go_live', service_id=current_service.id)
     )}}
 
-    <p>
+    <p class="govuk-body">
       Before you can use GOV.UK Notify, you need to accept our data sharing and financial agreement.
     </p>
-    <p>
+    <p class="govuk-body">
       This must be done by, or on behalf of, someone with the authority to sign contracts for {{ current_service.organisation.name }}.
     </p>
-    <p>
+    <p class="govuk-body">
       Once accepted, the agreement covers all Notify services from {{ current_service.organisation.name }}.
     </p>
-    <p>
+    <p class="govuk-body">
       <a class="govuk-link govuk-link--no-visited-state" href="{{ url_for('main.service_download_agreement', service_id=current_service.id) }}">Download a copy of the data sharing and financial agreement</a>.
     </p>
-    <p>
+    <p class="govuk-body">
       The agreement is confidential and should not be shared outside your organisation.
     </p>
     {{ govukButton({