feat: audit logging for Parseable

[nitisht]

Audit logging is a core requirement for enterprise software. We need to add a feature to ensure a Parseable server (in any mode - local, s3, standalone, distributed) sends out audit logs to a target specified via env vars.

Env variables to add:

• P_AUDIT_LOG_TARGET --> String, e.g. https://target.domain.name
• P_AUDIT_LOG_TARGET_USERNAME --> String, e.g. user
• P_AUDIT_LOG_TARGET_PASSWORD --> String, e.g. password
• P_AUDIT_LOG_TARGET_TLS_VERIFY --> Boolean, e.g. false
• P_AUDIT_LOG_TARGET_HEADERS --> Command separated key value pair (String:String,String:String), e.g. content-type:application/json, x-p-stream:audit

Also, we need to decide a schema of each audit log event. It should include version, eventType and other relevant details.