- Added new request models for datasource actions including validation, website crawling, and content retrieval.
- Enhanced `PluginExecutor` with methods to validate datasource credentials, crawl websites, and retrieve pages and content.
- Updated `PluginRegistration` to include methods for fetching datasource provider classes and handling website and online document datasources.
- Refined the `DatasourceProvider` interface to use `Mapping` for credentials, improving type safety.
- Introduced `OnlineDocumentDatasource` and `WebsiteCrawlDatasource` abstract classes for handling online document and website crawl functionalities.
- Added corresponding methods for retrieving pages and content, enhancing the datasource capabilities.
- Created new models for online document and website information to support the new interfaces.