Update claims instead of overwrite from webhook response

[3schwartz]

According to the webhook documentation:

To accept the token exchange without modification, return a 204 or 200 HTTP status code without a response body.

However, this behavior is currently not functioning as expected. When an empty response is returned, it overwrites the additional claims sent to the webhook, effectively erasing them.

Related issue(s)

#3879

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Further Comments

[CLAassistant]

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