Use named arguments for clearer string formatting

Helps when the string is long.

Also helps disambiguate between the CDN domain used for the logos and
those for CSS/JS.

app/main/views/email_branding.py

@@ -11,7 +11,7 @@ from app.main.s3_client import (
     persist_logo,
     upload_logo,
 )
-from app.utils import AgreementInfo, get_cdn_domain, user_is_platform_admin
+from app.utils import AgreementInfo, get_logo_cdn_domain, user_is_platform_admin
 
 
 @main.route("/email-branding", methods=['GET', 'POST'])
@@ -81,7 +81,7 @@ def update_email_branding(branding_id, logo=None):
         'views/email-branding/manage-branding.html',
         form=form,
         email_branding=email_branding,
-        cdn_url=get_cdn_domain(),
+        cdn_url=get_logo_cdn_domain(),
         logo=logo
     )
 
@@ -126,7 +126,7 @@ def create_email_branding(logo=None):
     return render_template(
         'views/email-branding/manage-branding.html',
         form=form,
-        cdn_url=get_cdn_domain(),
+        cdn_url=get_logo_cdn_domain(),
         logo=logo
     )
 

app/main/views/index.py

@@ -16,7 +16,7 @@ from app import email_branding_client
 from app.main import main
 from app.main.forms import SearchTemplatesForm
 from app.main.views.sub_navigation_dictionaries import features_nav
-from app.utils import AgreementInfo, get_cdn_domain
+from app.utils import AgreementInfo, get_logo_cdn_domain
 
 
 @main.route('/')
@@ -108,7 +108,7 @@ def email_template():
         colour = email_branding['colour']
         brand_name = email_branding['text']
         brand_colour = colour
-        brand_logo = ('https://{}/{}'.format(get_cdn_domain(), email_branding['logo'])
+        brand_logo = ('https://{}/{}'.format(get_logo_cdn_domain(), email_branding['logo'])
                       if email_branding['logo'] else None)
         govuk_banner = branding_type in ['govuk', 'both']
         brand_banner = branding_type == 'org_banner'

app/main/views/service_settings.py

@@ -54,7 +54,7 @@ from app.main.forms import (
 from app.utils import (
     AgreementInfo,
     email_safe,
-    get_cdn_domain,
+    get_logo_cdn_domain,
     user_has_permissions,
     user_is_platform_admin,
 )
@@ -991,7 +991,7 @@ def get_branding_as_value_and_label(email_branding):
 def get_branding_as_dict(email_branding):
     return {
         branding['id']: {
-            'logo': 'https://{}/{}'.format(get_cdn_domain(), branding['logo']),
+            'logo': 'https://{}/{}'.format(get_logo_cdn_domain(), branding['logo']),
             'colour': branding['colour']
         } for branding in email_branding
     }