feat(services/obs): support user defined metadata #8157

Job	Run time
build-haskell-doc	10m 47s
build-c-doc	14s
build-java-doc	18s
build-lua-doc	14s
build-nodejs-doc	20s
build-python-doc	3m 11s
build-rust-doc	3m 34s
build-dav-server-opendalfs-doc	46s
build-cpp-doc	15s
build-fuse3-opendal-doc	48s
build-object-store-opendal-doc	45s
build-ocaml-doc	4m 53s
build-parquet-opendal-doc	48s
build-unftp-sbe-opendal-doc	1m 10s
build-virtiofs-opendal-doc	43s
build-opendal-compat-doc	39s
build-website	1m 25s
	30m 50s

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