datetime format inconsistent in json files

[bernhardreiter]

A freshly run provider and aggregator write inconsistent datetime parameters (~v0.9.1), see examples

https://localhost:9443/.well-known/csaf-aggregator/aggregator.json

     "metadata": {
        "last_updated": "2022-06-09T10:52:03Z",
   }
  ],
  "last_updated": "2022-06-09T12:55:16+02:00"
}

https://localhost:8443/.well-known/csaf/white/csaf-feed-tlp-white.json

 "updated": "2022-06-09T16:40:27+02:00",
   "entry": [
      {

        "published": "2022-03-17T13:03:42Z",
        "updated": "2022-03-17T13:03:42Z",
"updated": "2022-03-17T13:03:42Z",

Expectation: should always be the UTC variant.

[Fadiabb]

Fixed with 714814a. Close here.