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/OptionsSpec.hs

@@ -1,6 +1,5 @@
 module Feature.OptionsSpec where
 
-import Network.Wai      (Application)
 import Network.Wai.Test (SResponse (..))
 
 import Network.HTTP.Types
@@ -10,8 +9,8 @@ import Test.Hspec.Wai
 import Protolude
 import SpecHelper
 
-spec :: SpecWith ((), Application)
-spec = describe "Allow header" $ do
+spec :: SpecWithConfig
+spec withConfig = withConfig baseCfg $ describe "Allow header" $ do
   context "a table" $ do
     it "includes read/write methods for writeable table" $ do
       r <- request methodOptions "/items" [] ""