Change log for MIMECAST_MAIL

Date Changes
2024-11-13 Enhancement:
- Mapped "URL" to "principal.url".
2024-08-05 Enhancement:
- Mapped "sourceIp" to "principal.ip" and "principal.asset.ip".
- Mapped "url" to "principal.url".
- Mapped "msgid" to "network.email.mail_id".
- Mapped "subject" to "network.email.subject".
- Mapped "senderDomain", "AttNames", and "AttCnt" to "security_result.detection_fields".
2023-03-31 Enhancement:
- Mapped "filename_for_malachite" to "principal.resource.name".
- Mapped "fileName" to "principal.process.file.full_path".
- Mapped "sha256" to "target.file.sha256".
- Mapped "sha1" to "target.file.sha1".
- Added conditional check for "aCode".