add: config client-error-verbosity to set error verbosity

Set error verbosity using this config. The verbosity can
be set to `verbose` or `minimal` for client error responses.

This only affects client side HTTP responses, server side logs
are not affected by this config.

Signed-off-by: Taimoor Zaeem <taimoorzaeem@gmail.com>

src/PostgREST/Config/Database.hs

@@ -46,6 +46,7 @@ dbSettingsNames :: [Text]
 dbSettingsNames =
   (prefix <>) <$>
   ["db_aggregates_enabled"
+  ,"client_error_verbosity"
   ,"db_anon_role"
   ,"db_pre_config"
   ,"db_extra_search_path"