Support Datasource (uid) as variable value for other Datasource

[genofire]

Is your feature request related to a problem? Please describe.
I like to link the datasource prometheus to a datasource tempo.
e.g. https://grafana.com/docs/grafana/latest/datasources/tempo/configure-tempo-data-source/

(If applicable)If your feature request solves a bug please provide a link to the community issue

Describe the solution you'd like

---
apiVersion: grafana.integreatly.org/v1beta1
kind: GrafanaDatasource
metadata:
  name: tempo
spec:
  valuesFrom:
    - targetPath: "jsonData.tracesToMetrics.datasourceUid"
      valueFrom:
        datasourceRef:
          name: prom
          fieldPath: metadata.uid
    - targetPath: "jsonData.serviceMap.datasourceUid"
      valueFrom:
        datasourceRef:
          name: prom
          fieldPath: metadata.uid
  instanceSelector:
    matchLabels:
      dashboards: "grafana"
  datasource:
    name: Tempo
    type: tempo
    url: http://localhost:3200
    access: proxy
    basicAuth: false
    jsonData:
      tracesToMetrics:
        datasourceUid: 'replaced-by-valueFrom'
      serviceMap:
        datasourceUid: 'replaced-by-valueFrom'

Describe alternatives you've considered
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Additional context
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Existing solutions
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[theSuess]

Thanks for the suggestion!

IMHO the solution would be to use consistent UIDs for the data sources using spec.uid. Would that work for your usecase?

We're investigating potential "generic value substition" methods but don't have anything specific in mind yet.