Set the CC email address for an event email context

Updates the CC email address applied to all event emails sent for the given context (practitioner or facility). This is a context-level setting: the address applies across both modes (credentialing and recredentialing) for this context. Sending a blank or null value clears the CC address and removes it from any nested mode-level records as well. Returns the full EventEmailSettingsContextResponse for the context, including both mode summaries — not just the updated CC field. A 400 is returned when the submitted value is not a valid email address format. Use this endpoint to change the CC address independently of the full mode settings; to set it as part of a full settings save, include it in the POST /{context}/{mode} body instead. Note: unlike the {context}/{mode} routes, this path does not constrain context to practitioner|facility at the routing layer or validate it in the service — other string values are silently accepted and stored as-is.