feature: support read config from etcd

[dk-lockdown]

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watch config key in etcd for dynamic update.

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[bohehe]

I'm interested in this issue and want to help, but I'm not sure what is the purpose of this issue.
Can you please explain more details regarding watch config key in etcd for dynamic update. ? Thanks.

[dk-lockdown]

The config file was refactored before, now with appid as the base unit, watch ${appid}/listeners、${appid}/executors、${appid}/datasources

[zeina1i]

Hey @dk-lockdown
I'm interested in implementing this :) If possible assign it to me