Ensure we only use x-default on appropriate pages (#15526)

* Remove hreflang="x-default" link from credits FAQ page

* Only show hreflang="x-default" if it's on the homepage for a locale

(Separately, the nonlocale root page at / also serves hreflang="x-default"
already, and this change does not affect that because it's got its own
template which does not use the canonical-url.html partial)

bedrock/base/templates/includes/canonical-url.html

@@ -7,7 +7,7 @@
 {%- set available_languages = get_locale_options(request, translations) -%}
 
     <link rel="canonical" href="{{ settings.CANONICAL_URL + '/' + LANG + canonical_path }}">
-    <link rel="alternate" hreflang="x-default" href="{{ settings.CANONICAL_URL }}{{ canonical_path }}">
+    {% if is_homepage %}<link rel="alternate" hreflang="x-default" href="{{ settings.CANONICAL_URL }}{{ canonical_path }}">{% endif %}
     {% if available_languages -%}
       {%- for code, label in available_languages|dictsort -%}
         {%- set alt_url = alternate_url(canonical_path, code) -%}

bedrock/mozorg/templates/mozorg/credits-faq.html

@@ -13,7 +13,6 @@
 
 {% block canonical_urls %}
   <link rel="canonical" href="{{ canonical_url }}">
-  <link rel="alternate" hreflang="x-default" href="{{ canonical_url }}">
 {% endblock %}
 
 {% block page_og_url %}{{ canonical_url }}{% endblock %}

bedrock/mozorg/views.py

@@ -133,6 +133,11 @@ class HomeView(L10nTemplateView):
 
     ftl_files_map = {old_template_name: ["mozorg/home"], template_name: ["mozorg/home-new"]}
 
+    def get_context_data(self, **kwargs):
+        ctx = super().get_context_data(**kwargs)
+        ctx.update({"is_homepage": True})
+        return ctx
+
     def get_template_names(self):
         experience = self.request.GET.get("xv", None)