Upgrade to Spring Boot 3 / Java 17 and add ThriftClientHeaderCustomizer hook

[rpajaziti]

What this PR does

This fork upgrades the library to Spring Boot 3 / Java 17 and adds a hook for custom header propagation on the client side.

Changes

Spring Boot 3 / Java 17 upgrade

• Migrated all dependencies and configuration to Spring Boot 3.2.5
• Updated to Java 17 source/target compatibility
• Replaced deprecated APIs and javax imports with jakarta equivalents

ThriftClientHeaderCustomizer hook

• New @FunctionalInterface that allows consumers to inject custom HTTP headers into every outgoing Thrift call without touching the library internals
• Called per method invocation so headers like transaction IDs are always fresh
• Headers are cleared automatically on pool return via existing passivateObject() cleanup
• The library has zero knowledge of what fills the hook — Seata XID, Brave trace headers, auth tokens, anything

Dependency version pinning

• All api dependencies in starter/build.gradle now have pinned versions
• Consumers no longer need to import the Spring Cloud or Spring Boot BOM to resolve transitive dependencies

Usage example

@Bean
public ThriftClientHeaderCustomizer seataHeaderCustomizer() {
    return () -> {                                                                                                                                                                                                                                                                                                           
        String xid = RootContext.getXID();
        return StringUtils.hasText(xid) ? Map.of(RootContext.KEY_XID, xid) : Map.of();                                                                                                                                                                                                                                       
    };                                                                                                                                                                                                                                                                                                                       
}