Explain Spring Boot 3.x major changes and migration considerations.

Spring Boot 3.x major changes:\n\n1) Java 17+ requirement\n2) Jakarta EE migration (javax.* → jakarta.*)\n3) Spring Framework 6.x\n4) Native image improvements\n5) Observability enhancements\n6) Virtual threads support\n\nMigration steps:\n1) Update Java to 17+\n2) Replace javax imports with jakarta\n3) Update dependencies\n4) Test thoroughly\n5) Update configuration if needed\n\nExample migration:\n// Before\nimport javax.persistence.Entity;\n// After\nimport jakarta.persistence.Entity;