USAGOV-2001 samlauth default config and stage config

[arpage]

Jira Task

https://cm-jira.usa.gov/browse/USAGOV-2001

Description

Add logic to samlauth config chooser script which will enable the SecureAuth configuration if there is no environment-specific config file.

Also, add GSAAuth config file for the stage environment.

Type of Changes

• New Feature
• Bugfix
• Frontend (Twig, Sass, JS)
  • Add screenshot showing what it should look like
• Drupal Config (requires "drush cim")
• New Modules (requires rebuild)
• Documentation
• Infrastructure
  • CMS
  • WAF
  • WWW
  • Egress
  • Tools
  • Cron
• Other

Testing Instructions

It would be difficult to test this PR as-is, because the 2 situations where it is currently applicable is:

1. In stage, where the effect of this PR is to enable GSAAuth SSO.
2. In prod, where the effect of this PR is to enable SecureAuth SSO.

Please note however, that the first commit successfully tested the "default" scenario (by renaming the DR config file).
The stage scenario has not been tested yet, as it would not work outside of the stage environment.

Change Requirements

• Requires New Documentation (Link: {})
• Requires New Config
• Requires New Content

Validation Steps

1. When deployed to stage, GSAAuth SSO should function as expected.
2. When deployed to prod, SecureAuth SSO should function as expected (unless this PR superceded by another, which provides the GSAAuth config for the prod environment).

Security Review

• Adds/updates software (including a library or Drupal module)
• Communication with external service
• Changes permissions or workflow
• Requires SSPP updates

Reviewer Reminders

• Reviewed code changes
• Reviewed functionality
• Security review complete or not required

Post PR Approval Instructions

Follow these steps as soon as you merge the new changes.

1. Go to the USAGov Circle CI project.
2. Find the commit of this pull request.
3. Build and deploy the changes.
4. Update the Jira ticket by changing the ticket status to Review in Test and add a comment. State whether the change is already visible on cms-dev.usa.gov and beta-dev.usa.gov, or if the deployment is still in process.

[akf]

Looks reasonable.