Show 404 page for documentation site

[aduth]

As part of the current effort to deprecate design.login.gov, show a 404 page in place of site contents, so that a user has resources to learn more about Login.gov or receive support.

Live preview: https://federalist-2f194a10-945e-4413-be01-46ca6dae5358.sites.pages.cloud.gov/preview/18f/identity-style-guide/aduth-docs-404/404.html

This is derived from the Login.gov main site 404 page: https://www.login.gov/404.html

Next steps:

• Revisions to _config.yml will not be committed, they are for demonstration only in the preview environment. The plan would be to configure these through Cloud.gov Pages interface
  • Configuration in 6982fbd will be applied in Cloud.gov Pages site admin
• Excluding content in the live environment will allow us to continue using the documentation site for internal testing and pull request previews
  • Follow-on work should plan to remove most documentation aside from component previews
  • At some point, we may remove all site content altogether, or simplify it such that we can remove the Jekyll build pipeline, or move everything to Login.gov Component Previews environment, or move package contents to be a workspace package within the 18f/identity-idp repository.

Draft while I sort out why Cloud.gov Pages doesn't show the 404 page by default. See #333 (comment)

[aduth]

I was struggling to get the 404 page to show up in the preview environment. Based on a related Slack comment, I believe Cloud.gov Pages will always try to use the production deployment's 404 page, hence why it's not yet showing up here.

Since the plan will be to apply the configuration reverted in 6982fbd in the Cloud.gov Pages Dashboard, merging this as-is won't actually remove any content from the site, but it will add the 404 page so that we can at least confirm it's working in production before applying the new configuration.

So effectively, this pull request simply adds a 404 page, but does not affect any other existing content.

[aduth]

The visual regression build failure reflects the change discussed at #333 (comment) .

Compare:

• Live brand guidance: https://design.login.gov/brand/
• Preview brand guidance: https://federalist-2f194a10-945e-4413-be01-46ca6dae5358.sites.pages.cloud.gov/preview/18f/identity-style-guide/aduth-docs-404/brand/

Before	After

[aduth]

Maybe we need to normalize the intrinsic sizes of those two images.

[aduth]

Maybe we need to normalize the intrinsic sizes of those two images.

In 608fde9, I recreated the reverse logo by taking the original and swapping out all the #112E51 with #ffffff 🤷

Preview: https://federalist-2f194a10-945e-4413-be01-46ca6dae5358.sites.pages.cloud.gov/preview/18f/identity-style-guide/aduth-docs-404/brand/

[nickttng]

In 608fde9, I recreated the reverse logo by taking the original and swapping out all the #112E51 with #ffffff 🤷

This approach works, and it looks good to me.

[zachmargolis]

LGTM

[zachmargolis]

does the docs dir already go to top level? do we need to add a permalink so that it's in the right place to be a 404 page for CG pages?

Suggested change

	layout: 404
	layout: 404
	permalink: /404.html

[aduth]

I think it's fine without? It seems to be available at /404.html already without specifying permalink.

[aduth]

Confirmed that the 404 configuration approach works.

Example†: https://federalist-2f194a10-945e-4413-be01-46ca6dae5358.sites.pages.cloud.gov/preview/18f/identity-style-guide/aduth-lgds-7/

I did this by adding the following configuration to the Preview Site configuration:

exclude:
  - '*'
include:
  - 404.html

To decommission the production site, we'll just add that configuration to the Live Site configuration.

---

† The broken image and styles are somewhat expected, for the same reason as described at #333 (comment) : Cloud.gov Pages 404 pages always use the live site's 404 page, which would include references to root-relative /assets/ that don't exist in the preview environment. It'll be fine on the live site, though.