Add authentication extension #722

Job	Run time
test-macos	50s
check	30s
doc	2m 3s
fmt	10s
test-ubuntu (-p stac)	45s
test-ubuntu-with-pgstac	1m 6s
test-ubuntu-with-gdal	1m 52s
test-windows	4m 31s
test-ubuntu (-p stac -F reqwest)	1m 35s
test-ubuntu (-p stac -F wkb)	1m 9s
validate-stac-server	1m 14s
test-ubuntu (-p stac-api)	39s
validate-stac-server-pgstac	1m 34s
test-ubuntu (-p stac -p stac-api -F geo)	1m 4s
test-ubuntu (-p stac-async)	1m 5s
test-ubuntu (-p stac-cli --no-default-features)	1m 23s
test-ubuntu (-p stac-server --no-default-features)	1m 3s
test-ubuntu (-p stac-server --no-default-features -F axum)	1m 25s
test-ubuntu (-p stac-server --no-default-features -F memory-item-search)	1m 34s
test-ubuntu (-p stac-server)	1m 1s
test-ubuntu (-p stac-validate)	56s
	27m 29s

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