Improve Mimecast parsing

[TonioRyo]

• Extract email subject
• Extract URL from rejection info

[github-actions]

Smart descriptions generated from the latest tests at 2025-01-09 16:27:32:

Test File	Smart Description
Mimecast/mimecast-email-security/tests/test_attachment_protect.json	{"processingId": "processingId", "aggregateId": "aggregateId", "sha1": "816b013c8be6e5708690645964b5d442c085041e", "accountId": "C0A0", "fileName": "tpsreport.docx", "sha256": "efe51c2453821310c7a34dca3054021d0f6d453b7133c381d75e3140901efd12", "fileExtension": "xlsm", "subType": null, "eventType": "attachment protect", "timestamp": 1689692409135, "md5": "4dbe9dbfb53438d9ce410535355cd973"}
Mimecast/mimecast-email-security/tests/test_av_logs.json	AV detected bad.virus.found in file NULL from auser@mimecast.com
Mimecast/mimecast-email-security/tests/test_delivery.json	Inbound email from john.doe@example.org to jane.doe@example.com
Mimecast/mimecast-email-security/tests/test_impersonation_protect.json	Hold email from auser@mimecast.com
Mimecast/mimecast-email-security/tests/test_internal_email_project.json	Restricted File Type - Found executable extension: dll on email from john.doe@example.org
Mimecast/mimecast-email-security/tests/test_journal.json	Inbound email from newsletter@stub.com to neo@gmail.fr
Mimecast/mimecast-email-security/tests/test_process.json	Hld email from john.doe015@gmail.com
Mimecast/mimecast-email-security/tests/test_process_with_attachment.json	Allow email from auser@mimecast.com
Mimecast/mimecast-email-security/tests/test_process_with_multiple_attachments.json	Acc email from johndoe@gmail.com
Mimecast/mimecast-email-security/tests/test_receipt.json	Acc Inbound email from john.doe@gmail.com to admin@mcfr2.pro
Mimecast/mimecast-email-security/tests/test_receipt_urls.json	Rej Inbound email from john.doe@gmail.com to admin@mcfr.pro
Mimecast/mimecast-email-security/tests/test_spam.json	Spam detected in email from john.doe@example.org to jane.doe@example.com
Mimecast/mimecast-email-security/tests/test_url_protect_blocked.json	Protected john@mcfr2.pro by Block URL http://www.mimcast.com

[squioc]

LGTM. Thanks for the improvements