Correct db settings to use "_" instead of "-"

GUC settings with dashes cannot be shown with show or current_setting.

https://www.postgresql.org/message-id/flat/20210209144059.GA21360%40depesz.com

src/PostgREST/Config.hs

@@ -477,18 +477,19 @@ readAppConfig dbSettings env optPath = do
                                (C.Key -> C.Parser C.Value a -> C.Parser C.Config b) ->
                                C.Key -> (C.Value -> a) -> C.Parser C.Config b
     overrideFromDbOrEnvironment necessity key coercion =
-      case reloadableDbSetting <|> M.lookup name env of
+      case reloadableDbSetting <|> M.lookup envVarName env of
         Just dbOrEnvVal -> pure $ justIfMaybe $ coercion $ C.String dbOrEnvVal
         Nothing  -> necessity key (coercion <$> C.value)
       where
-        name = "PGRST_" <> map capitalize (toS key)
-        capitalize '-' = '_'
-        capitalize c   = toUpper c
+        dashToUnderscore '-' = '_'
+        dashToUnderscore c   = c
+        envVarName = "PGRST_" <> (toUpper . dashToUnderscore <$> toS key)
         reloadableDbSetting =
-          if key `notElem` [
-            "server-host", "server-port", "server-unix-socket", "server-unix-socket-mode", "log-level",
-            "db-anon-role", "db-uri", "db-channel-enabled", "db-channel", "db-pool", "db-pool-timeout", "db-load-guc-config"]
-          then lookup key dbSettings
+          let dbSettingName = pack $ dashToUnderscore <$> toS key in
+          if dbSettingName `notElem` [
+            "server_host", "server_port", "server_unix_socket", "server_unix_socket_mode", "log_level",
+            "db_anon_role", "db_uri", "db_channel_enabled", "db_channel", "db_pool", "db_pool_timeout", "db_load_guc_config"]
+          then lookup dbSettingName dbSettings
           else Nothing
 
     coerceText :: C.Value -> Text