[Enhancement] Improve Error message when missing secrets

[dansiegel]

SUMMARY

Since we now know what secrets are expected for a given project, the Secrets Class Generator should fail with error messages for each property that is missing.

DETAILS

Given a configuration like the following

"projectSecrets": {
  "BuildToolsSample": {
    "className": "Settings",
    "namespace": "Helpers",
    "properties": [
      {
        "name": "AppCenterId",
        "type": "String"
      }
    ]
  }
}

We should see a build error like:

Missing Secret value for 'AppCenterId' when the property has not been defined in the secrets.json

PLATFORMS

n/a

[dansiegel]

This is resolved in the latest build