docs: Azure authentication refactoring design

[shahramk64]

Description

What this PR does / why we need it:

This PR proposes a design doc for refactoring Azure authentication modules in Ratify. It describes the existing Azure authentication modules and it's pain points and provide a solution to refactor the code to solve those pain points.

Which issue(s) this PR fixes (optional, using fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when the PR gets merged):

Provide a design doc to #1944

Type of change

Please delete options that are not relevant.

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] Helm Chart Change (any edit/addition/update that is necessary for changes merged to the main branch)
• [x] This change requires a documentation update

Checklist:

• [ ] Does the affected code have corresponding tests?
• [ ] Are the changes documented, not just with inline documentation, but also with conceptual documentation such as an overview of a new feature, or task-based documentation like a tutorial? Consider if this change should be announced on your project blog.
• [ ] Does this introduce breaking changes that would require an announcement or bumping the major version?
• [ ] Do all new files have appropriate license header?

Post Merge Requirements

• [ ] MAINTAINERS: manually trigger the "Publish Package" workflow after merging any PR that indicates Helm Chart Change

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

[susanshi]

Ready for review, maintainers please take another look @binbin-li , @akashsinghal , @susanshi

[codecov[bot]]

Codecov Report

:white_check_mark: All modified and coverable lines are covered by tests. :warning: Please upload report for BASE (dev@04d1de7). Learn more about missing BASE report.

Additional details and impacted files

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  Hits           ?     5422           
  Misses         ?     1454           
  Partials       ?      374           

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