feat(mongodb): Adding node selector to be passed through to mongo workloads

[alix-graylog]

Adding the same nodeSelector interface to mongodb, exposed to the charts values.yaml

# Graylog Datanode
# Already present
datanode:
  enabled: true
  nodeSelector:
    this/node_tier: data

# Mongo
# Newly Exposed
mongodb:
  communityResource:
    enabled: true
  nodeSelector:
    this/node_tier: data

Summary

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Details

• List of meaningful technical changes

Linked issues

This fixes #??

PR Checklist

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• Tests added/updated
• Documentation updated
• This PR includes a new feature
• This PR includes a bugfix
• This PR includes a refactor

Testing Checklist

Static Validation

• Linter check passes: helm lint ./charts/graylog
• Helm renders local template sucessfully: helm template graylog ./charts/graylog --validate

Installation

• Fresh installation completes successfully: helm install graylog ./charts/graylog
• All pods reach Running state: kubectl rollout status statefulset/graylog
• Helm tests pass: helm test graylog

Functional (if applicable)

• Web UI accessible and login works
• DataNodes visible in System > Cluster Configuration
• Inputs can be created and receive data

Upgrade (if applicable)

• Upgrade from previous release succeeds
• Scaling up/down works correctly
• Configuration changes apply correctly

Specific to this PR

• describe what was specifically tested

Notes for reviewers

• Verify all applicable tests above pass
• Validate that the linked issues are no longer reproducible, if applicable
• Sync up with the author before merging
• The commit history should be preserved - use rebase-merge or standard merge options when applicable