Maintenance API returns tags key in lower-case

We've been working with version 2018-06-01-preview of the Maintenance API's (via v38.1.0 of the Azure SDK for Go) - and have noticed a bug that the `tags` key returned from Azure is always lower-cased, regardless of the input case. For example if I create a Maintenance Configuration with tags
```
tags = {
"ENV": "prod"
}
```

the response of tags is always
```
tags = {
"env": "prod"
}
```
Would it be possible to update this API to return the `tags` in the correct case, rather than lower-casing it?

Thanks!

Start by locating the Maintenance API 2018-06-01-preview specification and the definition of its tags property. Reproduce the request with an ENV tag, then verify that the specification or relevant response example preserves the submitted case; done means the returned key remains ENV rather than becoming env.

Written by the indexing model from the issue text.