feat(cas-auth): support logged-in user header #16864

Job	Run time
build (ubuntu-20.04, linux_openresty, lua-resty-worker-events, t/plugin/[a-k]*)	34m 19s
build (ubuntu-20.04, linux_openresty, lua-resty-worker-events, t/plugin/[l-z]*)	37m 12s
build (ubuntu-20.04, linux_openresty, lua-resty-worker-events, t/admin t/cli t/config-center-yaml...	25m 29s
build (ubuntu-20.04, linux_openresty, lua-resty-worker-events, t/node t/pubsub t/router t/script ...	14m 10s
build (ubuntu-20.04, linux_openresty, lua-resty-events, t/plugin/[a-k]*)	34m 44s
build (ubuntu-20.04, linux_openresty, lua-resty-events, t/plugin/[l-z]*)	35m 43s
build (ubuntu-20.04, linux_openresty, lua-resty-events, t/admin t/cli t/config-center-yaml t/cont...	25m 46s
build (ubuntu-20.04, linux_openresty, lua-resty-events, t/node t/pubsub t/router t/script t/secre...	24m 12s
	3h 51m 35s

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