Spring-ai chore: Update dependencies and fix OpenAPI client generation

• Upgrade Spring Boot to 3.4.0
• Update swagger-codegen-maven-plugin to 3.0.64
• Add custom template for HttpBasicAuth
• Fix mockwebserver version to 4.12.0
• Fix parent version reference in opensearch-store

NOTE: Revert the boot to 3.3.6 before merging!!!

Comment From: tzolov

Changed the boot version to 3.3.6, rebased, squashed and merged at c05714881303e9b43ab710ec900cef11f3dbd9e4