Change log for ZIX_EMAIL_ENCRYPTION

Date Changes
2024-05-10 Enhancement:
- Mapped "Zix" as "metadata.vendor_name" and "Zix Email Encryption" as "metadata.product_name".
- Mapped "user_id" field to "principal.user.userid".
- Added a Grok pattern to parser unparsed logs.
2022-11-05 Newly created parser