API URL for migrations are no longer valid with latest release. It need to be replaced with mobility ( example, /migrations?action=validate with /mobility/migration/validate )

With new update, we can update IP address, subnet mask, gateway, DNS servers and even we can mark it as connected it or not as well as primary IP. Note, this feature can't be done via PowerCLI as it is only available with API.

I modified your modules and tried to insert all of these, but for some reason validation JSON do not show all of these and I get 400 error.

Error output as shown below. I had validated the input, all mandatory items are correctly came up in the input file, but not on the order as per the script. I did a test with correct order, but still same output. Attached my input file for reference.
Input.txt

{ "items": [ { "migrationId": "", "migrationGroupId": "", "errors": [ { "code": "E_INVALID_INPUT", "message": "Not all networks are configured." }, { "code": "E_INVALID_INPUT", "message": "Destination is not configured." }, { "code": "E_INVALID_INPUT", "message": "Placement is not configured." }, { "code": "E_INVALID_INPUT", "message": "Storage is not configured." }, { "code": "E_INVALID_INPUT", "message": "Entity is not configured." } ] } ] }