Add info.pattern for String and other minor fixes

[natanael]

1. Deduplicate info.description logic
2. Add info.pattern to Strings
3. Enable defaults for List and Enum Requires: https://github.com/oatpp/oatpp/pull/282 (already merged)

   DTO_FIELD_INFO(referral) {
   info->pattern = "^[^\\s]+$"; // This is what we set to add
   };
   DTO_FIELD(String, referral, "referral") = "direct";
   DTO_FIELD(List<String>, friends) = [](){
   auto defaultFriends = List<String>::createShared();
   defaultFriends->push_back(String("me")); // :)
   return defaultFriends;
   }(); // Poor-mans default, just for testing
   DTO_FIELD(Enum<HelloEnum>, helloEnum) = HelloEnum::V1; // We had it but it wasn't showing in swagger

   "referral": {
   "type": "string",
   "default": "direct",
   "pattern": "^[^\\s]+$" // <- Some tools can use this for validating the JSON
   },
   "friends": {
   "type": "array",
   "default": [ // <- Defaults for List<String>
       "me"
   ],
   "items": {
       "type": "string"
   }
   },
   "helloEnum": {
   "default": "value-1", // <- Defaults for Enum<T>
   "$ref": "#\/components\/schemas\/HelloEnum(String)"
   }

[lganzzzo]

This looks awesome! Please fix the minor comment, and I'll merge it.

[lganzzzo]

Aaaand it's merged 🎉

[bamkrs]

Keep up the good work!