Document changes to exported records

[korthout]

With command distribution, we have made several changes to the appended records. These changes will also be noticeable to exporters. We should document them in the update guide for 8.2 to 8.3.

The changes are:

• introduced CommandDistribution value type
  • records of this value type can have intents:
    • STARTED (event)
    • DISTRIBUTING (event)
    • ACKNOWLEDGE (command)
    • ACKNOWLEDGED (event)
    • FINISHED (event)
  • records of this value type may have the following properties:
    • partitionId
    • valueType
    • intent
    • commandValue
• deprecated DeploymentDistribution value type
  • new deployments are distributed with CommandDistribution records
  • in progress DeploymentDistribution started before 8.3.0-alpha3 can still result in records of this value type

Open question
I'm unsure whether we need to document the newly introduced value type in the update guide. The deprecation should be documented there because it may break the expectations of exporters. Additions should be documented somewhere, but we have no place for this at this time.

[remcowesterhoud]

Done with camunda/camunda-docs#2703