Allow ui_config.metrics.path_allowlist to be configured

[agrahamlincoln]

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Is your feature request related to a problem? Please describe.

It may be desirable to have a prometheus metrics provider hosted under a subpath. In this configuration, there's no way to configure the path_allowlist option to add a prefix to each of these paths. (More docs on Path Allowlist)

Feature Description

add a new option to the helm chart to enable operators to modify ui_config.metrics.path_allowlist to their liking

Use Case(s)

When prometheus metrics provider is hosted on a subpath

Example values.yaml for the helm chart (limited to only relevant config for this feature request):

global:
  metrics:
    enabled: true
ui:
  enabled: true
  metrics:
    baseUrl: http://consul-prometheus.consul.svc.cluster.local:9090/consul
    provider: prometheus

This configuration will never work and the server will throw errors in the log that look like the following:

[ERROR] agent.ui_metrics_proxy: target URL path is not allowed: base_url=http://consul-prometheus.consul.svc.cluster.local:9090/consul path=/api/v1/query target_url=http://consul-prometheus.consul.svc.cluster.local:9090/consul/api/v1/query path_allowlist=["/api/v1/query", "/api/v1/query_range"]

Contributions

Submitted a proposal for change in #4445