BE: Integrate Swagger UI for API documentation #631

[Rupa-421]

• Breaking change? (if so, please describe the impact and migration path for existing application instances)

What changes did you make? (Give an overview)
This PR integrates Swagger UI into the application using springdoc-openapi and automates the API contract delivery.
Key changes include:
Version Catalog Migration: Moved springdoc and related dependencies to libs.versions.toml for centralized management.
Build Automation: Created a new Gradle task copyOpenApiSpecForSwagger that automatically pulls the latest OpenAPI YAML from the contract-typespec module and places it in the static web resources.
Security Configuration: Updated the Security Filter Chain to permit access to Swagger UI endpoints (/swagger-ui/, /v3/api-docs/, etc.).
Application Properties: Configured springdoc to point to the local static OpenAPI spec instead of the default generated one to ensure consistency with the TypeSpec definition.
Resource Management: Linked processResources to the spec-copying task to ensure the UI is always up-to-date during development and packaging.
Fixes #631

Is there anything you'd like reviewers to focus on?

How Has This Been Tested? (put an "x" (case-sensitive!) next to an item)

• No need to
• Manually : Verified Swagger UI loads at /swagger-ui.html and correctly parses the kafbat-ui-api.yaml file. Verified that the static/openapi folder is correctly generated after a ./gradlew clean build.
• Unit checks
• Integration checks
• Covered by existing automation

Checklist (put an "x" (case-sensitive!) next to all the items, otherwise the build will fail)

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (e.g. ENVIRONMENT VARIABLES)
• My changes generate no new warnings (e.g. Sonar is happy)
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged

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[github-actions]

Hi Rupa-421! 👋

Welcome, and thank you for opening your first PR in the repo!

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[Rupa-421]

I have updated the PR to disable Swagger UI by default. It can now be toggled via the AUTH_OPENAPI_ENABLED environment variable. I also added the documentation for this variable in the README.md

[Haarolean]

@Rupa-421 have you tried running this with any kind of auth enabled? login_form should work fine, but I fear oauth might be tricky here

[Rupa-421]

@Haarolean ,I have tried with auth enabled for both the login form and also Github Oauth. They are working fine.