Authenticator: remove jwt.Validate

[drakkan]

jwt.Validate is already called in Verifier, no need to call it twice.

If jwt.Validate fails in Verifier, the error is set in the context and the Authenticator retrieves the token and error from the context.

[VojtechVitek]

LGTM. Makes sense.

Already called in Verifier:

jwtauth/jwtauth.go

Lines 114 to 116 in 127ee7c

	if err := jwt.Validate(token, ja.validateOptions...); err != nil {
	return token, ErrorReason(err)
	}