Enhance spring boot configuration metadata

[oxsean]

Why

Configuration beans of dubbo are located in the dubbo-common module, and it's not suitable to add spring boot dependencies.
However, spring configuration metadata generation relies on read javadoc from the source code and cannot use the @NestedConfigurationProperty annotation.
This leads to missing comments and a lack of nested configuration options. Therefore, we use an independent module to copy the code and generate metadata.

Principles

1. Copy classes under org/apache/dubbo/config from dubbo-common to the generated-sources directory.
2. Replace @Nest with @NestedConfigurationProperty.
3. Copy the class DubboConfigurationProperties.java from autoconfigure to the generated-sources directory.
4. Use an annotation-only option to compile and generate spring-configuration-metadata.json.
5. During autoconfigure module compilation, will read spring-configuration-metadata.json from this module.

How to add a new configuration option

• For standard configuration options, add javadoc to the corresponding configuration classes in dubbo-common.
• For non-standard configuration options, there are unnecessary to add nested classes. add them directly to additional-spring-configuration-metadata.json.

Preview

spring-configuration-metadata.json