Changes to Get SIEM-oriented summary of flagged message groups

added the optional property message_groups/items/attack_score_verdict to the response with the 200 status

added the optional property message_groups/items/first_reported_as_phish_at to the response with the 200 status

added the optional property message_groups/items/recipients to the response with the 200 status

added the optional property total to the response with the 200 status

added the optional property truncated to the response with the 200 status