New Sigma rules pipeline mapping for M365 and Fortigate

[marcopedrinazzi]

Hello, I've noticed that in the pipeline (https://github.com/Security-Onion-Solutions/securityonion/blob/33ada95bbce6fdfb45bee98b376a4a7662f8a830/salt/soc/files/soc/sigma_so_pipeline.yaml) that does the conversion from sigma to EQL in Security Onion 2.4.201 the fields in the sigma rules related to fortigate and m365 are not mapped.
Example Fortigate:

Example M365:

Therefore I've added these mappings, below you can find my updated version.

Let me know what you think about it

Thanks!
sigma_so_pipeline.yaml

[HBadger0017]

What directory does one load this yaml into? I'm working on similar additions for zeek:conn and zeek:modbus to expand into Operational Technology/ICS logs.

[marcopedrinazzi]

Pull request: #15579

[defensivedepth]

Thanks @marcopedrinazzi !

I will review your PR!