Okta configuration - missing guidance, and examples

[dboyd13]

• Missing guidance when setting up the Okta authorization server (default) you need to change the default Audience string from api://default to the one set in the Okta applications OpenID Connection ID Token
• Missing guidance of updating Okta Sign-in redirect URLsredirect_uri and Sig-out redirect URLs to point to the CloudFront URL

aws-iam-temporary-elevated-access-broker/README.md

Line 152 in ce85fa4

### Integrating with your identity provider

Overall, screenshots of example configurations would be valuable.

[cnmoise]

Hey I found this to be true as well, you can't get past the splash page without following these two steps

I may put in a pull request for this since I'm implementing this for a customer & writing accurate guides with 0 prereq knowledge is a passion of mine