Uppercase coverage value to pass validation

[alies-dev]

Description

The PR partially solves #172 by fixing coverage value for IntlVerification object

Note, there is a similar issue with setStatus but it's not possible to solve it in such an easy way, as a described in the issue:

it's not possible to fix \OpenAPI\Client\Model\IntlVerification::setStatus on this library level: when this method accept a numeric string (e.g. 1), we don't how to properly prefix the string because there are few possible prefixes (LV, LF, LM, LU. see the screenshot above). So, the only solution is to fix server response or lose IntlVerification validation in setCoverage and setStatus methods

So, ideally both issues should be solved on server level and this PR should be rejected. But if you think it's not possible to change server response for any reasons - this PR can be merged to fix at least one issue

[alies-dev]

The issue with coverage field is solved on API level, closing.

But the status field issue remains unsolved so far (in short: it returns a number like "2" instead of a string like "LF2" or "LV2" or "LM2")