Ensure AddonDocs doesn't break fastboot

[samselikoff]

Tried upgrading Storefront's AddonDocs to latest version, still ran into errors.

Did some digging, found these:

• https://github.com/ember-cli/ember-fetch/issues/55
• https://github.com/simplabs/ember-simple-auth/issues/1138

Only solution was to ember install ember-fetch to Storefront (as a devDependency, so just for the dummy app). Seems weird/broken to me, but if this is the only solution we should add to the docs?

[dfreeman]

The issue seems to be a mismatch in expectations between ember-fetch and ember-cli-fastboot. The former uses the updateFastBootManifest hook to add a Node-compatible version of fetch to the build, but that hook is only ever invoked for top-level addons, not nested ones.

The only thing I immediately saw in the issue tracker was a semi-related issue about fastbootDependencies not being recursively discovered, where @kratiahuja suggested that that hook might provide an alternative. If it's not being recursively invoked itself, though, then I'm not sure how these pieces are actually supposed to fit together ¯\_(ツ)_/¯

[dfreeman]

I think https://github.com/tchak/ember-fetch-adapter/issues/1 and https://github.com/ember-cli/ember-fetch/issues/98 are two more recent examples of this popping up specifically due to updateFastBootManifest rather than the older fastbootDependencies issue