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/OpenApi/RootSpec.hs

@@ -1,16 +1,19 @@
 module Feature.OpenApi.RootSpec where
 
 import Network.HTTP.Types
-import Network.Wai        (Application)
 
 import Test.Hspec          hiding (pendingWith)
 import Test.Hspec.Wai
 import Test.Hspec.Wai.JSON
 
-import Protolude hiding (get)
+import PostgREST.Config                  (AppConfig (..))
+import PostgREST.SchemaCache.Identifiers (QualifiedIdentifier (..))
 
-spec :: SpecWith ((), Application)
-spec =
+import Protolude  hiding (get)
+import SpecHelper
+
+spec :: SpecWithConfig
+spec withConfig = withConfig (baseCfg { configDbRootSpec = Just $ QualifiedIdentifier mempty "root" }) $
   describe "root spec function" $ do
     it "accepts application/openapi+json" $ do
       request methodGet "/"