Complete the introduction paragraph to the Swagger docs

[danieleguido]

We would like to add a bit of context to the swagger documentation page. /src/middleware/swagger.ts
Also @theorm is it possible to add service specific description?

[theorm]

@danieleguido it is possible to add service specific and endpoint specific descriptions. They are already there, but they are almost an exact copy of the title. I'm happy to add the descriptions if someone writes them.

[e-maud]

@theorm I can give it a go, will ping you on this.