Please check below all steps necessary to complete this ticket:
- Create a custom Storage Adapter, as DDMJSONStorageAdapter, implementing the interface DDMStorageAdapter, deploy it to branch master and check if the custom Storage Adapter is available on Form Settings (go to Content & Data > Forms > + button > Settings > Select a Storage Type).
- Make sure the custom Storage Adapter is persisting the data according to the new Storage Type, like XML, for instance.
- Verify if it's feasible to implement an automatic test (maybe an integration test?) to keep this extension point working as expected and avoid the need of a manual check.