Add a prototype email template

If the templates page contains text messages and emails then there’s two ways it
could be structured:
- into two sections, all text messages first, then all emails
- emails and text messages interleaved, sorted by date

I think the second one is better. Imagine a situation where you mostly do emails
but have a few text messages. You’d have to scroll past the text messages to get
to your emails. Every time.

I reckon that the most commonly accessed templates will be the most recent ones.

app/main/views/templates.py

@@ -4,7 +4,7 @@ from flask_login import login_required
 from app.main import main
 from app.main.forms import TemplateForm
 
-from ._templates import sms_templates, email_templates
+from ._templates import templates
 
 
 @main.route("/services/<int:service_id>/templates")
@@ -13,8 +13,7 @@ def manage_templates(service_id):
     return render_template(
         'views/manage-templates.html',
         service_id=service_id,
-        sms_templates=sms_templates,
-        email_templates=email_templates
+        templates=templates,
     )
 
 
@@ -35,14 +34,14 @@ def add_template(service_id):
         return redirect(url_for('.manage_templates', service_id=service_id))
 
 
-@main.route("/services/<int:service_id>/templates/<template_id>", methods=['GET', 'POST'])
+@main.route("/services/<int:service_id>/templates/<int:template_id>", methods=['GET', 'POST'])
 @login_required
 def edit_template(service_id, template_id):
 
     form = TemplateForm()
 
-    form.template_name.data = 'Reminder'
-    form.template_body.data = 'Vehicle tax: Your vehicle tax for ((registration number)) expires on ((date)). Tax your vehicle at www.gov.uk/vehicle-tax'  # noqa
+    form.template_name.data = templates[template_id - 1]['name']
+    form.template_body.data = templates[template_id - 1]['body']
 
     if request.method == 'GET':
         return render_template(