Description:

Describe the issue.

Raising this PR to make a decision on which client certs to use when originating a TLS connection to ext Auth and Backend TLS (relates to kubernetes-sigs/gateway-api#2743)

Option 1
Reuse Listener (Downstream) certs

Option 2
Define a common proxy cert in the EnvoyProxy config

Option 3 (not possible today)
Define certs in each config

• within the SecurityPolicy.ExtAuth.TLS field
• not possible in BackendTLS, since its a upstream API