main changes
1) add grin-schema，with no obvious conflict to pg-schema
2) add GRIN_TRAIT_LOOSE_SCHEMA and related api，to be compatible with strict/loose of pg-schema
3) refine label related apis
4) add external_id related apis, to support RDF graph in the future
5) add chain_list api, impl and test in grin extension
main changes 1) add grin-schema，with no obvious conflict to pg-schema 2) add GRIN_TRAIT_LOOSE_SCHEMA and related api，to be compatible with strict/loose of pg-schema 3) refine label related apis 4) add external_id related apis, to support RDF graph in the future 5) add chain_list api, impl and test in grin extension