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[GulajavaMinistudio]

• Caseless header comparing in HTTP adapter.

It was adding User-Agent and removing Authorization, but only when
existing headers had the exact right casing. Node uses caseless logic
when managing headers.

This was causing some requests to have User-Agent appended to the
headers object and overriding provided agent strings.

Also included is an update to not override the Content-Length if it
was already defined in the options. It can be desirable to manually
specify a content length that does not match the data on hand.
Especially for testing.

• Fix eslint error

• fixup: update state UA logic

Play nice with axios#3703

Co-authored-by: Jay jasonsaayman@gmail.com

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