docs: Add service documentation links and expand contributing guide

[DUSHIMEDanPaul]

• Added clickable links to service documentation (Keycloak, Elastic Search, nginx)
• Expanded 'Making a Code Changes' section with workflow, testing, and PR process details
• Removed TODO comments
• Improves onboarding for new contributors

Change(s)

Change Type:

Change Category:

Changelog Entry:

How to Test

Checklist

• Tests have been added or updated to reflect the changes, or their absence is explicitly explained.
• Documentation has been added or updated to reflect the changes, or their absence is explicitly explained.
• A self-review has been conducted checking:
  • No unintended changes have been committed.
  • The changes in isolation seem reasonable.
  • Anything that may be odd or unintuitive is provided with a GitHub comment explaining it (but consider if this should not be a code comment or in the documentation instead).
• All CI checks pass before pinging a reviewer, or provide an explanation if they do not.
• The PR title matches the changelog entry's one-line description.

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