Support login session, query payload, and multi events

[ryli17]

This PR is to resolve the following issues:

1. Authentication through another path
   For example, login through http://1.1.1.1/login, but query through http://1.1.1.1/query. After successfully logged in, session information is exchanged by cookies.
2. Each query may return multiple items.
   For example, one query may return a json object, such as {"entries":[{"message": "message 1"}, {"message":"message 2"}]}.
   The expected fluentd output is
   2020-09-01 12:00:00 tag: {"message":"message 1"}
   2020-09-01 12:00:00 tag: {"message":"message 2"}

Detailed usage please refer to README

[HatsuneMiku3939]

@ryli17

Thank you for your contribution. Can you provide a description of this PR?

I'll check the changes in 1~2 days.

[ryli17]

@HatsuneMiku3939 , Sorry for the delayed response. I added a brief description. Please let me know if any further info is needed. Thanks!