To avoid having to handle decision and process report definitions differently in the recent changes on the process definition with
OPT-4825 we agreed to align the decision report definition to also switch the `view.property` field to `view.properties`.
- a new field view.properties of type array is added to align this report type with the recent process data changes
- the current singular field view.property is kept for backwards compatibility, will be removed with
- existing reports are migrated using the upgrade script
- REST API documentation in Confluence is updated