Unexported fields in API structs lead to problems with API mocking

[vladimir-tryputska]

Is your feature request related to a problem? Please describe.
statuscale-go client has interfaces like UptimeAPI, which is great. It allows us to mock them in our unit tests. The problem is with structs like APICreateUptimeTestRequest or APIUpdateUptimeTestRequest, where fields are private and there are not read-access methods. So we cannot really validate in tests whether properties have valid values. Workaround would be to use httpmock, which raises a question of the necessity of the statuscake-go client in general. In this case we could use REST api.

Describe the solution you'd like
It would be great to have properties exported in structs like APICreateUptimeTestRequest or APIUpdateUptimeTestRequest