feat -- configurable homepage widgets

[B-T-D]

Summary of Changes

Refactors existing features on the home page to be widgets, and adds ability for Amundsen instances to customize their widgets.

Tests

Modified some home page tests to reflect refactor.

Documentation

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[Golodhros]

We probably want this bundled inside the SearchWidget

[B-T-D]

I agree conceptually but would like to leave that change until a little later if you don't mind--it'll require some tweaking beyond just moving the Breadcrumb to be inside a different render, since elsewhere in the UI we render the search bar without the "Advanced Search" Breadcrumb, for example on the advanced search page itself ('/search' URL):

(screenshot from our prod)

[Golodhros]

There are several approaches to this, you can see 'generateHomepageWidgets()' functions around, and also having new components rendered:
I favor the last one, but the former is common in Amundsen's codebase too.

[B-T-D]

What do you mean by having new components rendered? A new HomePageWidgetContainer (or whatever name) component that holds all the widgets that the user wants on their homepage? That seems logical to me.

[B-T-D]

So it could be something like:

  render() {
    /* TODO, just display either popular or curated tags,
    do we want the title to change based on which
    implementation is being used? probably not */
    return (
      <main className="container home-page">
        <div className="row">
          <div
            className={`col-xs-12 ${
              announcementsEnabled() ? 'col-md-8' : 'col-md-offset-1 col-md-10'
            }`}
          >
            <h1 className="sr-only">{HOMEPAGE_TITLE}</h1>
            ****<HomePageWidgets
               getHomePageWidgets={getHomePageWidgets} 
             />****
          </div>
          {announcementsEnabled() && (
            <div className="col-xs-12 col-md-offset-1 col-md-3">
              <Announcements />
            </div>
          )}
        </div>
      </main>
    );
  }
}

[Golodhros]

Yes, but you don't need to extract it into a different file for the moment, you can write it above line 40 as a functional component.

[B-T-D]

Thanks, will do!

[Golodhros]

LGTM