Upgrade path for deprecated element templates

[sbuettner]

Is your feature request related to a problem? Please describe.

The deprecation feature that is currently available as part of the element-template schema only supports a documentation and text messages.

It would be helpful to allow to define am migrationElementTemplateId as part of the deprecation that can be used as an upgrade path. This would allow to migrate from a deprecated element-template to a another one.

Describe the solution you'd like

Supporting migration paths could be integrated into the deprecated object in addition to the already supported message:

...
  "deprecated": {
    "message": "This template is not supported anymore. Please migrate",
    "migrationElementTemplateId": "my-new-element-template-id"
  },
...

A "migrate" option is given to the user, and activating it will use the standard replace mechanism to upgrade.

Describe alternatives you've considered

An alternative would be to link to the new element template in the existing text fields but this require additional work and would for example not support an automatic migration to another element template without user interaction.

[nikku]

This would offer additional user guidance for our migration journey, which is currently manual, i.e. not tool supported.

To better understand your use-case: Under the hood this would still be a normal "replace with other task", using our existing upgrade behavior?

[sbuettner]

Yes, exactly.

[nikku]

Thanks. Updated the issue accordingly. Moving to backlog for the time being. To be prioritized.