automatically infer validation and swagger docs from types
### Is your feature request related to a problem? Please describe.

RIght now, when typing a PathParam or a property with an enum, we need to write: `@PathParams('campaignListType') @Enum(CampaignListType) campaignListType: CampaignListType`. Why do we need to write `@Enum(CampaignListType)` explicitly? Can't we infer the validation and swagger documentation automatically from the type?