fastify declaration merging for requests

fastify-request-declaration-merge.ts

// https://github.com/fastify/help/issues/122
import fastify from 'fastify'

declare module 'fastify' {
  interface FastifyRequest<
    HttpRequest,
    Query = fastify.DefaultQuery,
    Params = fastify.DefaultParams,
    Headers = fastify.DefaultHeaders,
    Body = any
  > {
    user: string
  }
}