Include `selectable` boolean in `/terminology/entry/{id}/relations` response

[Shayan1375]

Description

Currently, the /terminology/entry/{id}/relations endpoint returns detailed information about a terminology entry, including its children, parents, translations, and related terms. There should be an additionall boolean selectable to each entry (children, parents, and related terms) indicating whether the entry can be selected in the frontend.
Example response:

{
  "display": {
    "original": "display entry",
    "translations": [
      {
        "language": "de-DE",
        "value": "localized entry"
      }
    ]
  },
  "parents": [
    {
      "name": "Endokrine, Ernährungs- und Stoffwechselerkrankungen",
	"selectable": true,
      "contextualizedTermcodeHash": "c55d0d62-6c47-30b0-94b2-afa383ce35f7"
    }
  ],
  "children": [
    {
      "name": "Endokrine, Ernährungs- und Stoffwechselerkrankungen",
	"selectable": true,
      "contextualizedTermcodeHash": "c55d0d62-6c47-30b0-94b2-afa383ce35f7"
    }
  ],
  "relatedTerms": [
    {
      "name": "Endokrine, Ernährungs- und Stoffwechselerkrankungen",
	"selectable": false,
      "contextualizedTermcodeHash": "c55d0d62-6c47-30b0-94b2-afa383ce35f7"
    }
  ]
}

[michael-82]

I think the best way would be to already include this information in the files from the ontology generator. It can be done in the backend via elastic search, but would cause lots of additional queries or joins which I would advise against.