Add integration tests for `RecipientActivation`: `GetActivationUrlInfo`, `RetrieveToken`

Please add integration tests for the following APIs:

 - https://docs.databricks.com/api/workspace/recipientactivation/getactivationurlinfo
 - https://docs.databricks.com/api/workspace/recipientactivation/retrievetoken