[feat] bc-db: add current ud

lib/modules-lib/bc-db-reader/src/current_metadata.rs

...dules-lib/bc-db-reader/src/current_metadata/current_ud.rs

lib/modules-lib/bc-db-reader/src/traits.rs

lib/modules/blockchain/bc-db-writer/src/current_metadata.rs

lib/modules/blockchain/bc-db-writer/src/writers/requests.rs