Fix: Regional Admin is Logged Out When Viewing an Organization

[Matthew-Grayson]

🗣 Description

• Add regionalAdmin to RouteGuard for /organizations/:organizationId
• Add checks to associated endpoint to verify a user is a regionalAdmin and that a selected organization belongs to their region
• Add missing awaits to save() methods in organizations.ts
• Simplify if statements in auth.ts

💭 Motivation and context

Fix issue #268

🧪 Testing

✅ Pre-approval checklist

• This PR has an informative and human-readable title.
• Changes are limited to a single goal - eschew scope creep!
• All future TODOs are captured in issues, which are referenced
  in code comments.
• All relevant type-of-change labels have been added.
• I have read the CONTRIBUTING document.
• These code changes follow cisagov code standards.
• All relevant repo and/or project documentation has been updated
  to reflect the changes in this PR.
• Tests have been added and/or modified to cover the changes in this PR.
• All new and existing tests pass.

✅ Pre-merge checklist

• Revert dependencies to default branches.
• Finalize version.

✅ Post-merge checklist

• Create a release.

[cduhn17]

LGTM

[schmelz21]

LGTM