Add minimal OTel Agent container

[levan-m]

What does this PR do?

Minimal OTel agent setup with some defaults in Operator. It's enabled by otelAgentEnabled argument (disabled by default) but enabled for local testing in this branch here.

Added two TODO items where custom volume mounts and env vars should be added.

To run locally you'll need Kind cluster and Go 1.22:

# Create a local Kind cluster

# build image
make build && make docker-build

# load image in the kind cluster
kind load docker-image --name mycluster $(make -s echo-img)

# deploy
make deploy

# switch to default installation namespace
kubens system

# create secret
kubectl create secret generic datadog-secret --from-literal api-key=API_KEY

# apply DatadogAgent manifest
kubectl apply -f agent.yaml

I used following manifest for tests, it has custom command, env var and image tag overrides for illustration

apiVersion: datadoghq.com/v2alpha1
kind: DatadogAgent
metadata:
  name: datadog-agent
spec:
  global:
    credentials:
      apiSecret:
        secretName: datadog-secret
        keyName: api-key
      appSecret:
        secretName: datadog-secret
        keyName: app-key
    clusterName: otel-test
    kubelet:
      tlsVerify: false
  features:
    logCollection:
      enabled: true
  override:
    nodeAgent:
      image:
        name: gcr.io/datadoghq/agent:7.54.0
      containers:
        otel-agent:
          command:
            - /bin/sleep
            - "300"
          env:
          - name: DD_LOG_LEVEL
            value: "debug"

Resulting OTel container

  - command:
    - /bin/sleep
    - "300"
    env:
    - name: KUBERNETES
      value: "yes"
    - name: DD_CLUSTER_AGENT_ENABLED
      value: "true"
    - name: DD_CLUSTER_AGENT_KUBERNETES_SERVICE_NAME
      value: datadog-agent-cluster-agent
    - name: DD_CLUSTER_AGENT_TOKEN_NAME
      value: datadog-agent-token
    - name: DD_KUBERNETES_KUBELET_HOST
      valueFrom:
        fieldRef:
          apiVersion: v1
          fieldPath: status.hostIP
    - name: DD_CLUSTER_NAME
      value: kind-rc2
    - name: DD_SITE
      value: datadoghq.com
    - name: DD_LOG_LEVEL
      value: debug
    - name: DD_KUBELET_TLS_VERIFY
      value: "false"
    - name: DD_CLUSTER_AGENT_AUTH_TOKEN
      valueFrom:
        secretKeyRef:
          key: token
          name: datadog-agent-token
    - name: DD_API_KEY
      valueFrom:
        secretKeyRef:
          key: api-key
          name: datadog-secret
    - name: DD_APP_KEY
      valueFrom:
        secretKeyRef:
          key: app-key
          name: datadog-secret
    - name: DD_DOGSTATSD_SOCKET
      value: /var/run/datadog/dsd.socket
    - name: DD_REMOTE_CONFIGURATION_ENABLED
      value: "true"
    image: gcr.io/datadoghq/agent:7.54.0
    imagePullPolicy: IfNotPresent
    name: otel-agent
    resources: {}
    terminationMessagePath: /dev/termination-log
    terminationMessagePolicy: File
    volumeMounts:
    - mountPath: /var/log/datadog
      name: logdatadog
    - mountPath: /etc/datadog-agent/auth
      name: datadog-agent-auth
      readOnly: true
    - mountPath: /etc/datadog-agent
      name: config
    - mountPath: /var/run/datadog
      name: dsdsocket
    - mountPath: /host/var/run
      name: runtimesocketdir
      readOnly: true
    - mountPath: /host/proc
      name: procdir
      readOnly: true
    - mountPath: /var/run/secrets/kubernetes.io/serviceaccount
      name: kube-api-access-rtqb5
      readOnly: true

Motivation

What inspired you to submit this pull request?

Additional Notes

Anything else we should know when reviewing?

Minimum Agent Versions

Are there minimum versions of the Datadog Agent and/or Cluster Agent required?

• Agent: vX.Y.Z
• Cluster Agent: vX.Y.Z

Describe your test plan

Write there any instructions and details you may have to test your PR.

Checklist

• [ ] PR has at least one valid label: bug, enhancement, refactoring, documentation, tooling, and/or dependencies
• [ ] PR has a milestone or the qa/skip-qa label

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 15.94203% with 58 lines in your changes missing coverage. Please review.

Project coverage is 54.87%. Comparing base (76d9786) to head (c647c57). Report is 355 commits behind head on main.

Files with missing lines	Patch %	Lines
...ontrollers/datadogagent/component/agent/default.go	0.00%	43 Missing :warning:
...lers/datadogagent/feature/enabledefault/feature.go	40.90%	11 Missing and 2 partials :warning:
main.go	0.00%	2 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1269      +/-   ##
==========================================
- Coverage   54.97%   54.87%   -0.11%     
==========================================
  Files         243      243              
  Lines       28058    28120      +62     
==========================================
+ Hits        15426    15430       +4     
- Misses      11759    11815      +56     
- Partials      873      875       +2     

Flag	Coverage Δ
unittests	54.87% <15.94%> (-0.11%)	:arrow_down:

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
controllers/datadogagent/controller.go	59.50% <100.00%> (+0.24%)	:arrow_up:
controllers/datadogagent/feature/types.go	26.92% <ø> (ø)
controllers/setup.go	56.66% <100.00%> (+0.36%)	:arrow_up:
main.go	0.00% <0.00%> (ø)
...lers/datadogagent/feature/enabledefault/feature.go	29.08% <40.90%> (-0.82%)	:arrow_down:
...ontrollers/datadogagent/component/agent/default.go	0.00% <0.00%> (ø)

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