Refactor persistence_test and move API call retry to API Service

[lwolczynski]

Under certain circumstances (starting a continuedAsNew workflow is one of them) it might take time before Temporal/Candace API calls can be resolved successfully and expected data is returned. We should refactor the code and retry API calls when a certain response is received (for example: 500 response)

ACs:

• Retry API calls when certain responses are received
  • TODO: Need to decide on checking error types, and backoff strategy
• Refactor persistence_test.go so it does not need to use Sleep.time method