Add sync doc generation to an existing NestJS project

[inigomarquinez]

The OpenAPI specification is a language-agnostic definition format used to describe RESTful APIs. Nest provides a dedicated module which allows generating such a specification by leveraging decorators.

Apart from that, it has a plugin that enhances the TypeScript compilation process to reduce the amount of boilerplate code required.

However, this doesn't come with the default boilerplate, so it would be good to include it and also add de swagger decorators automatically to the controllers (at least for the default controller included in the scaffolding).