jest-koa-mocks: allow configuring subdomainOffset on koa's app instance

[falkenhawk]

Overview

Please allow passing subdomainOffset which would then be set on the koa app's instance inside createContext function. Maybe customProperties could be used for that. This is necessary to control how ctx.subdomains array is constructed from requested url. https://koajs.com/#settings

Type

• [x] New feature
• [x] Changes to existing features

Motivation

What inspired this feature request? What problems were you facing, or what else makes you think this should be in quilt?

I think that's the only thing which is missing to fully mock the koa's context object.

[falkenhawk]

it just struck me I can still configure it after creating the mock...:

      const ctx = createMockContext({ url, headers });
      ctx.app.subdomainOffset = subdomainOffset;
      console.log(ctx.subdomains); // now resolved with passed subdomainOffset