Update to protolude 0.3.0

The good part is that protolude 0.3.0 builds with GHC 8.10.

The bad part is that this change is a bit painful:
- the default `toS` has changed to no longer convert to and from ByteString
- similarly, `show` no longer outputs ByteString

The changes here are pretty much minimal to keep things compiling; I didn't
see a nice way to work with the new ConvertText class, even though `toUtf8`
seems like it might help if used besides `toS` at just the right spots.

src/PostgREST/OpenAPI.hs

@@ -32,7 +32,8 @@ import PostgREST.Types      (Column (..), ForeignKey (..), PgArg (..),
                              PrimaryKey (..), ProcDescription (..),
                              Proxy (..), Table (..), toMime)
 import Protolude            hiding (Proxy, dropWhile, get,
-                             intercalate, (&))
+                             intercalate, toLower, toS, (&))
+import Protolude.Conv       (toS)
 
 makeMimeList :: [ContentType] -> MimeList
 makeMimeList cs = MimeList $ map (fromString . toS . toMime) cs