Fix link-to-external for integration tests

Since link-to-external is currently registered manually, integration tests that test components using link-to-external wind up having problems since it can’t be resolved.

One current solution is for developers to manually import the component and register it, which requires reaching into the -private internals of ember-engines (obviously non-ideal).

I’m unsure of the best way to solve this issue. My thinking currently is that the best way would be to enable ember-engines/resolver to have knowledge of resolving it’s special components (currently only the modified link-to and link-to-external).

[ezy]

Having come from working on Jest where common methodology is stubbing components that are dependancies but not required in the test, I followed the same approach in my Ember integration test. Was a nice easy way to get around the error.

hooks.beforeEach(function() {
    const externalLinkStub = class LinkToExternalComponent extends Component {};
    this.owner.register('component:link-to-external', externalLinkStub);
});

[nickiaconis]

I tried the suggested workaround, like so:

import LinkToExternalComponent from 'ember-engines/-private/link-to-external-component';

module('my-component', 'Integration | Component | my-component', {
  beforeEach() {
    this.registry.register('component:link-to-external', LinkToExternalComponent);
  },
});

which alleviates the assertion failure:

Assertion Failed: A helper named ‘link-to-external’ could not be found

but results in a type error:

TypeError: owner._getExternalRoute is not a function

being thrown from line 16 of the link component:

https://github.com/dgeb/ember-engines/blob/master/addon/-private/link-to-external-component.js#L16