Checklist

• The PR conforms to DataHub's Contributing Guideline (particularly Commit Message Format)
• Links to related issues (if applicable)
• Tests for the changes have been added/updated (if applicable)
• Docs related to the changes have been added/updated (if applicable)

Adds metadata ingestion as a disabled-by-default helm component of Datahub's kubernetes deployment.
This component will render a Kubernetes CronJob resource for each cron resource specified.

Metadata-ingestion configuration recipes must be supplied by the consumer of this chart as a mounted volume and then explicitly referenced by the crawlerConfigPath.

An example is as follows:

datahub-crawler:
  enabled: true
  crons:
    - name: "hive"
      schedule: "0 0 * * *" 
      crawlerConfigPath: "/var/crawler-config.yml"  
      extraVolumes:
        - name: config-volume
          configMap:
            name: hive-crawler-config  
      extraVolumeMounts:  
        - name: config-volume        
          mountPath: "/var/crawler-config.yml"
          subPath: config.yml
    - name: "postgres"
      schedule: "0 1 * * *" 
      crawlerConfigPath: "/var/crawler-config.yml"  
      extraVolumes:
        - name: config-volume
          configMap:
            name: postgres-crawler-config  
      extraVolumeMounts:  
        - name: config-volume        
          mountPath: "/var/crawler-config.yml"
          subPath: config.yml

With the appropriate ConfigMaps holding each concrete recipes deployed to Kubernetes, this example will generate 2 separate cronJob resources in Kubernetes, allowing for reuse of this component for however may metadata ingestion cron jobs may be required.

Test method:

• Successfully rendered valid Kubernetes resource which works as intended when deployed to a cluster.