test(spec): inline config into test suite

Previously, information about each test-suite was repeated in 3 separate
places:
- as a label and as implicit knowledge in the test-suite itself,
- as a comment in Main.hs, and
- as a configuration in SpecHelper.hs.

With this change, there will be a single source of truth in the test
suite itself. This will allow a single test-suite to easily test
multiple different configurations.

test/spec/Feature/NoSuperuserSpec.hs

@@ -1,15 +1,14 @@
 module Feature.NoSuperuserSpec where
 
-import Network.Wai (Application)
-
 import Network.HTTP.Types
 import Test.Hspec
 import Test.Hspec.Wai
 
 import Protolude
+import SpecHelper
 
-spec :: SpecWith ((), Application)
-spec =
+spec :: SpecWithConfig
+spec withConfig = withConfig baseCfg $
   describe "No Superuser" $ do
     it "proves that the authenticator role is not a superuser" $ do
       request methodGet "/rpc/is_superuser"