v1.5.0 Add types for this.db and this.context

[astorije]

I am currently doing exactly this to store the authenticated user info on the Apollo context: https://www.apollographql.com/docs/apollo-server/security/authentication/#putting-authenticated-user-info-on-the-context

Then, in the datasource, one would want to fetch something based on that user info:

  findMyFruits() {
    if (!this.context.user) {
      throw new AuthenticationError("you must be logged in");
    }

    return this.knex
      .select()
      .from<Fruit>("fruits")
      .where({ userId: this.context.user.id });
  }

By correctly typing the context of the datasource, this avoids some awkward typing such as (this.context as any).user as User.

And while I was at it anyway, I figured I'd help with #68 :)

[cvburgess]

Thank you! Will merge and ship this 🙏

[astorije]

Amazing, thank you!