feat(jwt) : add feature to jwt plugin:allow set headers from claim

[mtparet]

Summary
Add feature to jwt plugin: allow set header from claims.

Reopenning of #4761 #5713

Full changelog

[Implement] jwt plugin: allow set header from claims
if you configure headers_to_set(set) , headers with prefix "X-Jwt-Claim-" will be set to the response. For example, if 'sub' and 'app' are configured, and both of them are found in jwt's claims, two headers will be set to the response: X-Jwt-Claim-Sub and X-Jwt-Claim-App.

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[hanshuebner]

Looks good, but a test, changelog file and an entry to the removed_fields list is required to accommodate for the schema change. The test should cover that the headers_to_set configuration is handled properly when not specified as well as a variety of sensible configuration values.

Also, you need to sign our CLA.

@jschmid1 any thoughts from you as the subject matter expert?

[hanshuebner]

We don't generally create extra tables for local constants. Please change this to just

Suggested change

	local consts = {
	JWT_CLAIM_HEADER_PREFIX = "X-Jwt-Claim"
	}
	JWT_CLAIM_HEADER_PREFIX = "X-Jwt-Claim"

[hanshuebner]

If you rename the function to set_headers_from_claims, the comment is no longer needed.