[tk:backend] Test metadata validation retro compatibility

[ascariandrea]

To be sure the validation of metadata output is compatible with old versions of our metadata we need to dump some data from production DB and test it locally.
When we're sure we've covered all the possible cases we can release it (again).

Proposed Solution

Use the implementation of walkPaginatedRequest to walk all the metadata results returned by the api and add a decode step to identify which item is not valid.
In this phase we shouldn't fix issues on the parser side, but only changing how the object is patched in metadata.io.ts