IBX-6602: Used Content::getThumbnail directly for obtaining thumbnails

[ViniTou]

https://issues.ibexa.co/browse/IBX-6602

Dropped ContentThumbnail resolver usage

There is no need for it, as thumbnails can be obtained directly from Content::getThumbnail or User::getThumbnail.
Done this way, instead of doing user.getContent(), as accessing content from user object is deprecated.

Fixed UserItem (and UserGroupItem)

As it had type: "UserItem" but it was resolved to value it was not UserItem, but actual User object.

Added Thumbnail for user object

As it is possible now, to obtain thumbnails by accessing content on user object like this:

{
  content {
    folder(contentId: 81) {
      _contentInfo {
        owner {
          id
          content {
            _thumbnail {
              uri
            }
          }
        }
      }
    }
  }
}

accessing content on user is deprecated (since 6,10 ;) ), so new property was added to match php API

{
  content {
     folder (contentId: 81) {
       id,
      _contentInfo {
        owner{
          thumbnail {
            uri,
          },
        }
      }
     }
  }
}

Fixed unpacking object to array:

resolve: "@=resolver('ContentTypesFromGroup', {'groupId': value.id})"

This was just not working, and can be tested with

{
_repository {
    contentTypes {
      groups {
        contentTypes {
          name
        }
      }
    }
  }
}  

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
0.0% Duplication

[tomaszszopinski]

QA approved on IbexaDXP 4.5 commerce.

[bdunogier]

Looks good to me. Great PR description 10/10 :)