User Story:

As an SRE, I want to aggregate the `cluster_proxy_ca_expiry_timestamp` metric to achieve feature parity with OSD/ROSA clusters as they are today.

Acceptance Criteria:

Description of criteria:

• cluster_proxy_ca_expiry_timestamp is added as a metric to hypershift operator
• cluster_proxy_ca_expiry_timestamp is exported to RHOBS for alerting and monitoring

Engineering Details:

The expiry in classic is calculated by looking at the user supplied CA bundle, running openssl command to extract the expiry, and calculating the number of days that the cert is valid for. We should use the same approach to calculate the expiry for HCP clusters.

Current implementation:

• https://github.com/openshift/osd-metrics-exporter/blob/main/controllers/configmap/configmap_controller.go#L70-L91
• https://github.com/openshift/osd-metrics-exporter/blob/main/pkg/metrics/aggregator.go#L80-L85

SRE Spike for this effort: https://issues.redhat.com/browse/OSD-15414