Add "switch-based" public access decorator

When applied, this makes a view publicly available *if* the
settings.UNAUTHENTICATED_ACCESS switch is True; otherwise you
must be authenticated. This will be useful to propagate to
most other views to make this settings switch globally effective
at some point.

config/settings/base.py

@@ -27,7 +27,7 @@ PROJECT_VERSION = '2.5.1'
 # Unauthenticated access ------------------------------------------------------
 # This variable should eventually control whether unauthenticated access is
 # allowed *ANYWHERE* on this service, except the home page, which is always
-# public. For now, it just controls the API.
+# public. For now, it just controls the API and the public alerts page.
 UNAUTHENTICATED_ACCESS = True
 
 # Miscellaneous settings ------------------------------------------------------

gracedb/ligoauth/decorators.py

+import logging
+
 from django.conf import settings
 from django.contrib.auth import REDIRECT_FIELD_NAME
 from django.contrib.auth.decorators import user_passes_test
 from django.core.exceptions import PermissionDenied
-import logging
 
+# Set up logger
 logger = logging.getLogger(__name__)
 
 
@@ -48,3 +50,17 @@ def lvem_observers_only(function=None, login_url=None, superuser_allowed=False,
     if function:
         return actual_decorator(function)
     return actual_decorator
+
+
+def public_if_public_access_allowed(function=None, login_url=None,
+    raise_exception=False):
+
+    # Either unauthenticated access is allowed or if not,
+    # the user is authenticated
+    test_func = lambda u: \
+        settings.UNAUTHENTICATED_ACCESS or u.is_authenticated
+    actual_decorator = user_passes_test(test_func, login_url=login_url)
+
+    if function:
+        return actual_decorator(function)
+    return actual_decorator