In order to migrate to a newer version of the API you can use a custom HTTP header specifying the API version you would like to request. This allows you to stay on an earlier version and test your development environments against new versions and upgrade when ready.
The Fidel-Version header allows you define in each request the version of the endpoint output. It is possible to request the current version or newer versions of the API.
curl -X GET \ https://api.fidel.uk/v1/transactions/9cc66ebe-8a18-4a00-b9cb-e1802bc6709d \ -H 'content-type: application/json' \ -H 'fidel-key: sk_test_50ea90b6-2a3b-4a56-814d-1bc592ba4d63' \ -H 'fidel-version: 2019-03-05'