Fix environment variable substitution and enhance Azure Managed Identity SQL demo#1

Copilot wants to merge 3 commits intoappmod/java-managed-identity-spring/mi-azuresql-spring-20250909120600richposada/java-migration-copilot-samples:appmod/java-managed-identity-spring/mi-azuresql-spring-20250909120600from

copilot/fix-81e1d3c0-68c7-4015-8280-319bbeebee6arichposada/java-migration-copilot-samples:copilot/fix-81e1d3c0-68c7-4015-8280-319bbeebee6aCopy head branch name to clipboard