Change log for MANDIANT_CUSTOM_IOC

Date Changes
2023-12-19 - Mapped "threat.threat_feed_name" to "Mandiant".
2023-12-07 - Mapped "first_seen" to "metadata.interval.start_time".
- When "type" is "fqdn/ipv4/url", then mapped "custom_ioc_expire_date" to "metadata.interval.end_time".
- Mapped "threat_rating.threat_score" to "entity.entity.labels".
- Mapped "threat_rating.severity_level" to "threat.severity".
- Mapped "threat_rating.confidence_level" to "threat.confidence".
- Mapped "verdict_simple.timestamp" to "verdict_info.verdict_time".
- When "verdict_simple.verdict" is "malicious", then set "verdict_info.verdict_response" to "MALICIOUS".
- Mapped "verdict_info.verdict_type" based on "verdict_simple.verdict_source".
- Mapped "category" to "threat.category_details".
- Mapped "threat_rating.confidence_score" to "threat.confidence_details".
- Mapped "threat_rating.threat_score" to "threat.risk_score".
2023-11-17 Newly created parser.