[abnormal_security] Add Support for Not Analyzed Messages in Abuse Mailbox

[cpascale43]

Description

The integration currently captures abuse campaigns but does not include messages that were not analyzed. Customers have requested support for the /abuse_mailbox/not_analyzed endpoint to include these messages.

Proposed Solution

• Create a separate data stream for not analyzed messages.
• Implement API calls to the /v1/abuse_mailbox/not_analyzed endpoint to fetch details of messages that were not analyzed.
• Map the response fields to ensure compatibility with existing data streams.

API Reference

• Not Analyzed Messages API

Additional Notes

• The structure of not analyzed messages is different from abuse campaigns, so a separate data stream is necessary.
• The implementation is estimated to be straightforward (XS to S complexity).

[elasticmachine]

Pinging @elastic/security-service-integrations (Team:Security-Service Integrations)