Currently each email sent call will start a SMTP connection and drop it after finish.

Use SMTP pooled connection to enhance the performance

Slack chat: https://redhat-internal.slack.com/archives/C0233N2MBU6/p1720538277333569

Have to finish it by August

This needs those steps:

• Implement using pooling SMTP connections, POC here - https://gitlab.cee.redhat.com/insights-platform/backoffice-proxy/-/merge_requests/141
  • Add isIdle condition into retry logic
  • Don't use parameter and switch logic 
  • Stress testing Stage with observing message:
    • check message:  "Connection was idle: false" -If found multiple times -   it probably means we would need more max connections.
    • check message: "SMTP: Count of available connections: 1/3/100" -  available/active/max
• Promote into prod with current settings of maxConnections and observe usage - 
  • check messages as described in stress testing in stage and update maxConnections accordingly.
• Add more pods into production