[charts/csm-authorization] Add metrics support for proxy-server

[AkshaySainiDell]

Is this a new chart?

No

What this PR does / why we need it:

Adds Helm chart support for exposing the CSM Authorization proxy-server Prometheus metrics endpoint. This is the deployment-side companion to the proxy-server metrics instrumentation: it wires the X_CSI_METRICS_* environment variables, creates a Kubernetes Service, and optionally creates a ServiceMonitor for Prometheus Operator integration.

Special notes for your reviewer:

Checklist:

[Place an '[x]' (no spaces) in all applicable fields. Please remove unrelated fields.]

• Chart Version bumped
• Variables are documented in the chart README.md
• Title of the PR starts with the chart name (e.g. [charts_dir/mychartname]) if applicable

Testing

• Authorization installed with metrics enabled and the /metrics endpoint on proxy-server port :2112 was verified to emit the metrics below.
• Authorization installed metrics disabled and verified metrics server was not started.

Sample /metrics output

# HELP dell_csm_auth_credential_shield_total Total credential shielding results.
# TYPE dell_csm_auth_credential_shield_total counter
dell_csm_auth_credential_shield_total{status="success",storage_type="powermax"} 3

# HELP dell_csm_auth_quota_check_total Total quota check results.
# TYPE dell_csm_auth_quota_check_total counter
dell_csm_auth_quota_check_total{result="denied",storage_type="powermax",tenant="test-auth-tenant"} 1

# HELP dell_csm_auth_request_duration_seconds Authorization request duration in seconds.
# TYPE dell_csm_auth_request_duration_seconds histogram
dell_csm_auth_request_duration_seconds_bucket{storage_type="powermax",tenant="test-auth-tenant",le="0.1"} 1
dell_csm_auth_request_duration_seconds_bucket{storage_type="powermax",tenant="test-auth-tenant",le="0.5"} 3
dell_csm_auth_request_duration_seconds_bucket{storage_type="powermax",tenant="test-auth-tenant",le="1"} 3
dell_csm_auth_request_duration_seconds_bucket{storage_type="powermax",tenant="test-auth-tenant",le="2"} 3
dell_csm_auth_request_duration_seconds_bucket{storage_type="powermax",tenant="test-auth-tenant",le="5"} 3
dell_csm_auth_request_duration_seconds_bucket{storage_type="powermax",tenant="test-auth-tenant",le="10"} 3
dell_csm_auth_request_duration_seconds_bucket{storage_type="powermax",tenant="test-auth-tenant",le="30"} 3
dell_csm_auth_request_duration_seconds_bucket{storage_type="powermax",tenant="test-auth-tenant",le="60"} 3
dell_csm_auth_request_duration_seconds_bucket{storage_type="powermax",tenant="test-auth-tenant",le="+Inf"} 3
dell_csm_auth_request_duration_seconds_sum{storage_type="powermax",tenant="test-auth-tenant"} 0.428803408
dell_csm_auth_request_duration_seconds_count{storage_type="powermax",tenant="test-auth-tenant"} 3

# HELP dell_csm_auth_request_total Total authorization requests.
# TYPE dell_csm_auth_request_total counter
dell_csm_auth_request_total{status="failure",storage_type="powermax",tenant="test-auth-tenant"} 2
dell_csm_auth_request_total{status="failure",storage_type="powermax",tenant="unknown"} 2
dell_csm_auth_request_total{status="success",storage_type="powermax",tenant="test-auth-tenant"} 1

# HELP dell_csm_auth_role_access_total Total role access decisions.
# TYPE dell_csm_auth_role_access_total counter
dell_csm_auth_role_access_total{decision="allow",role="test-auth-role",storage_type="powermax"} 1

# HELP dell_csm_auth_success_rate Rolling ratio of successful authorization requests to total requests (0.0-1.0). Target: >0.95.
# TYPE dell_csm_auth_success_rate gauge
dell_csm_auth_success_rate 0.2

# HELP dell_csm_auth_token_validation_total Total token validation outcomes.
# TYPE dell_csm_auth_token_validation_total counter
dell_csm_auth_token_validation_total{reason="invalid_header",result="failure"} 1
dell_csm_auth_token_validation_total{reason="invalid_token",result="failure"} 1
dell_csm_auth_token_validation_total{reason="ok",result="success"} 4

# HELP dell_csm_auth_up 1 if the CSM Authorization proxy is running.
# TYPE dell_csm_auth_up gauge
dell_csm_auth_up 1

[bharathsreekanth]

Please update the description with the details.

[bharathsreekanth]

update description, testing details etc

[AkshaySainiDell]

update description, testing details etc

Updated the PR description to clearly capture the implemented changes and associated testing details.

[bharathsreekanth]

Minor comment added.