[Backend] Emit audit event to HTTP destination

Proposal

Once this issue is complete, namespaces that have set an external destination for their audit logs should see those audit logs being sent to their chosen destination.

Implementation Plan

• Create a new sidekiq worker to handle sending the audit log.
• Data about the project or group emitting the event should exist within the JSON payload.
• When any new audit log is created, the AuditEventService should asynchronously send the data that is written to log/audit_log.json to the desired HTTP endpoint.