Add common authentication methods to Logstash Output

[jamesagarside]

At current the Logstash Output for the ESF does not support authentication methods other than Username:Password.
Based on common Logstash use cases I see with my customers the output should also support TLS, PKI and Client Certificates.

Functionbeat has this functionality but goes EoL this October leaving no options for customers who use the above authentication methods with a Serverless Cloud Native mindset.

[ChrisEke]

Is it on the roadmap to add support for presenting client certificates with ESF?
We're also looking into migrating from Functionbeat to ESF and the lack of this functionality affects our security posture.