Use a demo site banner to avoid confusion

src/registrar/config/settings.py

@@ -146,7 +146,6 @@ STATICFILES_DIRS = [
     BASE_DIR / "assets",
 ]
 
-# TODO: decide on template engine and document in ADR
 TEMPLATES = [
     {
         "BACKEND": "django.template.backends.django.DjangoTemplates",
@@ -168,11 +167,16 @@ TEMPLATES = [
                 "django.contrib.messages.context_processors.messages",
                 "registrar.context_processors.language_code",
                 "registrar.context_processors.canonical_path",
+                "registrar.context_processors.is_demo_site",
             ],
         },
     },
 ]
 
+# IS_DEMO_SITE controls whether or not we show our big red "TEST SITE" banner
+# underneath the "this is a real government website" banner.
+IS_DEMO_SITE = True
+
 # endregion
 # region: Database----------------------------------------------------------###
 

src/registrar/context_processors.py

@@ -21,3 +21,13 @@ def canonical_path(request):
     template itself, so we do it here and pass the information on.
     """
     return {"CANONICAL_PATH": request.build_absolute_uri(request.path)}
+
+
+def is_demo_site(request):
+    """Add a boolean if this is a demo site.
+
+    To be able to render or not our "demo site" banner, we need a context
+    variable for the template that indicates if this banner should or
+    should not appear.
+    """
+    return {"IS_DEMO_SITE": settings.IS_DEMO_SITE}

src/registrar/templates/base.html

@@ -103,6 +103,20 @@
       </div>
     </div>
   </section>
+  {% if IS_DEMO_SITE %}
+    <section
+    class="usa-site-alert usa-site-alert--emergency usa-site-alert--no-icon"
+    aria-label="Site alert,,,,,"
+    >
+      <div class="usa-alert">
+        <div class="usa-alert__body">
+          <p class="usa-alert__text">
+            <strong>TEST SITE</strong> - Do not use real personal information. Demo purposes only.
+          </p>
+        </div>
+      </div>
+    </section>
+  {% endif %}
 
 
   {% block usa_overlay %}<div class="usa-overlay"></div>{% endblock %}