k8sattributes processor - Allow metadata extractions to be null

[clheikes]

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

I'd like to extract annotations and not be required to extract metadata fields as well.

    processors:
      k8sattributes/metrics:
        extract:
          annotations:
          - from: namespace
            key: splunk.com/metrics-index
            tag_name: com.splunk.index
          - from: pod
            key: splunk.com/metrics-index
            tag_name: com.splunk.index
          metadata: [k8s.pod.name] 

Describe the solution you'd like

Allow me to set metadata: null or something similar

Describe alternatives you've considered

As a workaround I'm setting metadata to a field that my pod assocation rule is using

Additional context

opentelemetry-collector-contrib/processor/k8sattributesprocessor/options.go

Line 73 in bc9e9ba

if len(fields) == 0 {

[github-actions]

Pinging code owners: @owais @dmitryax. See Adding Labels via Comments if you do not have permissions to add labels yourself.

[mcdoker18]

I am going to fix this bug after merging the PR.

setting of metadata to null or empty value in the config will cleanup default metadata values.

[github-actions]

This issue has been inactive for 60 days. It will be closed in 60 days if there is no activity. To ping code owners by adding a component label, see Adding Labels via Comments, or if you are unsure of which component this issue relates to, please ping @open-telemetry/collector-contrib-triagers. If this issue is still relevant, please ping the code owners or leave a comment explaining why it is still relevant. Otherwise, please close it.

Pinging code owners:

• processor/k8sattributes: @owais @dmitryax

See Adding Labels via Comments if you do not have permissions to add labels yourself.

[github-actions]

This issue has been inactive for 60 days. It will be closed in 60 days if there is no activity. To ping code owners by adding a component label, see Adding Labels via Comments, or if you are unsure of which component this issue relates to, please ping @open-telemetry/collector-contrib-triagers. If this issue is still relevant, please ping the code owners or leave a comment explaining why it is still relevant. Otherwise, please close it.

Pinging code owners:

• processor/k8sattributes: @dmitryax @rmfitzpatrick

See Adding Labels via Comments if you do not have permissions to add labels yourself.

[dmitryax]

Requires open-telemetry/opentelemetry-collector#4001 to be resolved first