docs: Fix default values of optional args for prometheus operator
This commit also improves the explanation of the config variable
etcd_endpoints.
@@ -124,12 +124,12 @@ Now visit [http://localhost:19090/graph](http://localhost:19090/graph).
|-------- |--------------|---------|----------|
| `namespace` | Namespace to deploy the prometheus operator into. | - | true |
| `grafana_admin_password` | Password for `admin` user in Grafana. | - | true |
-| `etcd_endpoints` | Endpoints of etcd reachable from Kubernetes. | - | false |
+| `etcd_endpoints` | List of endpoints via which etcd can be reachable from Kubernetes. | [] | false |
| `prometheus_operator_node_selector` | Node selector to specify nodes where the Prometheus Operator pods should be deployed. | {} | false |
| `prometheus_metrics_retention` | Time duration Prometheus shall retain data for. Must match the regular expression `[0-9]+(ms\|s\|m\|h\|d\|w\|y)` (milliseconds seconds minutes hours days weeks years). | `10d` | false |
-| `prometheus_external_url` | The external URL the Prometheus instances will be available under. This is necessary to generate correct URLs. This is necessary if Prometheus is not served from root of a DNS name. | - | false |
+| `prometheus_external_url` | The external URL the Prometheus instances will be available under. This is necessary to generate correct URLs. This is necessary if Prometheus is not served from root of a DNS name. | "" | false |
| `prometheus_node_selector` | Node selector to specify nodes where the Prometheus pods should be deployed. | {} | false |
| `alertmanager_retention` | Time duration Alertmanager shall retain data for. Must match the regular expression `[0-9]+(ms\|s\|m\|h)` (milliseconds seconds minutes hours). | `120h` | false |
-| `alertmanager_external_url` | The external URL the Alertmanager instances will be available under. This is necessary to generate correct URLs. This is necessary if Alertmanager is not served from root of a DNS name. | - | false |
+| `alertmanager_external_url` | The external URL the Alertmanager instances will be available under. This is necessary to generate correct URLs. This is necessary if Alertmanager is not served from root of a DNS name. | "" | false |
| `alertmanager_config` | Provide YAML file path to configure Alertmanager. See [https://prometheus.io/docs/alerting/configuration/#configuration-file](https://prometheus.io/docs/alerting/configuration/#configuration-file). | `{"global":{"resolve_timeout":"5m"},"route":{"group_by":["job"],"group_wait":"30s","group_interval":"5m","repeat_interval":"12h","receiver":"null","routes":[{"match":{"alertname":"Watchdog"},"receiver":"null"}]},"receivers":[{"name":"null"}]}` | false |
| `alertmanager_node_selector` | Node selector to specify nodes where the AlertManager pods should be deployed. | {} | false |
