Python: Add a new web demo application: Amazon Cognito identity pools

[AWS-LanDing]

This pull request adds a web-based demo application that demonstrates Amazon Cognito identity pools authentication flows, allowing users to interactively explore both enhanced and basic authentication flows with various identity providers.

Key Features

• Interactive Flow Comparison : Side-by-side demonstration of enhanced vs basic authentication flows
• Multi-Provider Support : Integration with Google, Facebook, Amazon, OIDC, SAML, Cognito user pools, and custom developer providers
• Real-Time API Visualization : Step-by-step visualization of actual AWS API calls with request/response data
• Guest Access Demo : Unauthenticated identity pool access patterns
• Developer Authentication : Custom developer provider authentication flows

Technical Implementation

• Backend : Python Flask application with modular authentication flow handlers
• Frontend : Vanilla JavaScript with dynamic UI and API flow visualization
• Architecture : Clean separation between enhanced and basic flow implementations
• Security : Proper credential handling and OAuth flow management

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By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[brmur]

@AWS-LanDing

1. I've added the Application label (Which gets rid of the first error). You correctly don't have permissions to add labels. This is normally done by our oncall, who triages PRs, adds appropriate labels, and assigns a reviewer. Once the review is complete, the reviewer will add the OnCall review needed label.

2. I looked into the WRITEME issue.
   a) Firstly, you haven't added this example to the metadata, so it won't appear in the Cognito Identity Pool chapter in the code library, or the Code examples for Amazon Cognito Identity chapter in the Cognito Developer Guide. If that suits your use case, that's okay. But for one-off examples like this, we usually recommend adding a descriptive page about your example to both of these. See https://w.amazon.com/bin/view/AWSDocs/CodeExamples/ManagingSnippets/#HAddmetadata Block Content tab.
   b) Strange that you're getting the WRITME error as there was no metadata, so nothing to change. Therefore you shouldn't be getting a WRITME error. It may be that your branch has some merge conflicts but more likely an error in the WRITEME tool that we have to address. Either way, I suggest merging the PR below (in response 3) first, and (optionally) adding the block content (in response 1) first. Then re-run the WRITEME tool, per these instructions, and check it runs successfully before merging your changes with this PR . Then we'll revisit the WRITME issue if required.

3. There's a third error - see https://github.com/awsdocs/aws-doc-sdk-examples/actions/runs/16915402875/job/47927905176?pr=7549 . The commenting around the licensing text in 3 of the JS files is causing a problem. I've added a PR to your fork/branch to correct this.