Add option to disable generating `defaultResolvers`

[koenpunt]

I can totally understand the use of the generated defaultResolvers, but it would be nice to have an option to disable them.

For example a project I'm working on doesn't use them, but now when I rename a property of a type, I have to generate the resolver types just because the defaultResolvers are using invalid properties.

[jasonkuhrt]

but now when I rename a property of a type, I have to generate the resolver types just because the defaultResolvers are using invalid properties.

If I understand correctly, take the following example, imagine I'm not using the default resolvers and imagine I change my model type such that it affects the parent herein... that could cause parent.first and parent.last to become invalid.

export namespace HumanNameResolvers {
  export const defaultResolvers = {
    first: (parent: HumanName) => parent.first,
    last: (parent: HumanName) => parent.last,
  }

  //...

  export interface Type {
    first: (
          parent: HumanName,
          args: {},
          ctx: Context,
          info: GraphQLResolveInfo
        ) => string | Promise<string>)
      

    last: (
          parent: HumanName,
          args: {},
          ctx: Context,
          info: GraphQLResolveInfo
        ) => string | Promise<string>)
      
  }
}

[jasonkuhrt]

Should work in the upcoming release:

# graphqlgen.yml
default-resolvers: false