Extend /api/load to support labels assignment

[tikolakin]

Is your feature request related to a problem? Please describe. We heavily use labels to organise test cases. Yet, label assignment is purely a manual approach. To leverage our test automation process we want to be able to assign labels to test at a time of test code synchronisation with testomatio So that test cases sent will appear with labels in testomatio

Describe the solution you'd like Allow providing labels I the request payload to /api/load endpoint ex.

{
  ...
  tests: [
    {
       "name": "string",
       "suites": [...],

       "code": "string",

       "skipped": true,

       "file": "string",
       "label": "chrome"
    }
  ]
}

Describe alternatives you've considered Currently, we have a script that assigns labels after test sync. Yet such an approach is suffering from the concurrent modification of test cases after import and potentially creates errors on your backend

Additional context Note: that API spec is no longer available at https://testomatio.github.io/api/load