fix(kube-stack): inject prometheus receiver when targetAllocator enabled without scrape_configs_file

When `scrape_configs_file` is empty and `targetAllocator.enabled: true`,
the OpenTelemetry Operator expects a `prometheus` receiver in the
collector config so it can patch in the `target_allocator` endpoint.
Without it, reconciliation fails with:
  "no prometheus available as part of the configuration"

This change injects a minimal prometheus receiver (empty scrape_configs)
when one isn't already defined, and appends `prometheus` to the metrics
pipeline receivers so target-allocator scraped metrics flow through.

Fixes #2210

Author: cyrille-leclerc

charts/opentelemetry-kube-stack/Chart.yaml

@@ -1,6 +1,6 @@
 apiVersion: v2
 name: opentelemetry-kube-stack
-version: 0.15.0
+version: 0.15.1
 description: |
   OpenTelemetry Quickstart chart for Kubernetes.
   Installs an operator and collector for an easy way to get started with Kubernetes observability.

charts/opentelemetry-kube-stack/examples/cloud-demo/rendered/bridge.yaml

@@ -5,7 +5,7 @@ kind: OpAMPBridge
 metadata:
   name: example
   labels:
-    helm.sh/chart: opentelemetry-kube-stack-0.15.0
+    helm.sh/chart: opentelemetry-kube-stack-0.15.1
     app.kubernetes.io/version: "0.151.0"
     app.kubernetes.io/managed-by: Helm
     release: "example"    

charts/opentelemetry-kube-stack/examples/cloud-demo/rendered/collector.yaml

@@ -6,7 +6,7 @@ metadata:
   name: example-daemon
   namespace: default
   labels:
-    helm.sh/chart: opentelemetry-kube-stack-0.15.0
+    helm.sh/chart: opentelemetry-kube-stack-0.15.1
     app.kubernetes.io/version: "0.151.0"
     app.kubernetes.io/managed-by: Helm
     release: "example"        

charts/opentelemetry-kube-stack/examples/cloud-demo/rendered/hooks.yaml

@@ -61,4 +61,4 @@ spec:
           - "delete"
           - "instrumentations,opampbridges,opentelemetrycollectors"
           - "-l"
-          - "helm.sh/chart=opentelemetry-kube-stack-0.15.0"
+          - "helm.sh/chart=opentelemetry-kube-stack-0.15.1"

charts/opentelemetry-kube-stack/examples/cloud-demo/rendered/instrumentation.yaml

@@ -5,7 +5,7 @@ kind: Instrumentation
 metadata:
   name: example
   labels:
-    helm.sh/chart: opentelemetry-kube-stack-0.15.0
+    helm.sh/chart: opentelemetry-kube-stack-0.15.1
     app.kubernetes.io/version: "0.151.0"
     app.kubernetes.io/managed-by: Helm
     release: "example"    

charts/opentelemetry-kube-stack/examples/daemonset-annotation-discovery-logs/rendered/collector.yaml

@@ -6,7 +6,7 @@ metadata:
   name: example-daemon
   namespace: default
   labels:
-    helm.sh/chart: opentelemetry-kube-stack-0.15.0
+    helm.sh/chart: opentelemetry-kube-stack-0.15.1
     app.kubernetes.io/version: "0.151.0"
     app.kubernetes.io/managed-by: Helm
     release: "example"        

charts/opentelemetry-kube-stack/examples/daemonset-annotation-discovery-logs/rendered/hooks.yaml

@@ -61,4 +61,4 @@ spec:
           - "delete"
           - "instrumentations,opampbridges,opentelemetrycollectors"
           - "-l"
-          - "helm.sh/chart=opentelemetry-kube-stack-0.15.0"
+          - "helm.sh/chart=opentelemetry-kube-stack-0.15.1"

charts/opentelemetry-kube-stack/examples/daemonset-annotation-discovery-metrics/rendered/collector.yaml

@@ -6,7 +6,7 @@ metadata:
   name: example-daemon
   namespace: default
   labels:
-    helm.sh/chart: opentelemetry-kube-stack-0.15.0
+    helm.sh/chart: opentelemetry-kube-stack-0.15.1
     app.kubernetes.io/version: "0.151.0"
     app.kubernetes.io/managed-by: Helm
     release: "example"        

charts/opentelemetry-kube-stack/examples/daemonset-annotation-discovery-metrics/rendered/hooks.yaml

@@ -61,4 +61,4 @@ spec:
           - "delete"
           - "instrumentations,opampbridges,opentelemetrycollectors"
           - "-l"
-          - "helm.sh/chart=opentelemetry-kube-stack-0.15.0"
+          - "helm.sh/chart=opentelemetry-kube-stack-0.15.1"

charts/opentelemetry-kube-stack/examples/daemonset-annotation-discovery/rendered/collector.yaml

@@ -6,7 +6,7 @@ metadata:
   name: example-daemon
   namespace: default
   labels:
-    helm.sh/chart: opentelemetry-kube-stack-0.15.0
+    helm.sh/chart: opentelemetry-kube-stack-0.15.1
     app.kubernetes.io/version: "0.151.0"
     app.kubernetes.io/managed-by: Helm
     release: "example"