Adds UserType owner field to NamespaceType

What does this MR do and why?

Adds owner field of UserType to NamespaceType

query:

{
  project(fullPath: "root/projectX") {
    namespace {
      owner {
        name
      }
    }
  }
}

response:

{
  "data": {
    "project": {
      "namespace": {
        "owner": {
          "name": "Administrator"
        }
      }
    }
  }
}

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