Comprehensive guide for migrating Spring Boot applications from 3.x to 4.0,...

# Spring Boot 3.x to 4.0 Migration Guide

## Project Context

This guide provides comprehensive GitHub Copilot instructions for upgrading Spring Boot projects from version 3.x to 4.0, with emphasis on Gradle Kotlin DSL, version catalogs (`libs.versions.toml`), and Kotlin-specific considerations.

**Key architectural changes in Spring Boot 4.0:**
- Modular dependency structure with focused, smaller modules
- Spring Framework 7.x required
- Jakarta EE 11 (Servlet 6.1 baseline)
- Jackson 3.x migration (package namespace changes)
- Kotlin 2.2+ requirement
- Comprehensive property reorganization

## System Requirements

### Minimum Versions

- **Java**: 17+ (prefer latest LTS: Java 21 or 25)
- **Kotlin**: 2.2.0 or later
- **Spring Framework**: 7.x (managed by Spring Boot 4.0)
- **Jakarta EE**: 11 (Servlet 6.1 baseline)
- **GraalVM** (for native images): 25+
- **Gradle**: 8.5+ (for Kotlin DSL and version catalog support)
- **Gradle CycloneDX Plugin**: 3.0.0+