curl --request POST \
  --url https://api.upon-ai.com/api/knowledge-bases/{knowledgeBaseId}/sources \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "workspaceId": 123,
  "sources": [
    {
      "text": "<string>",
      "title": "<string>",
      "url": "<string>",
      "filename": "<string>",
      "contentType": "<string>",
      "base64": "<string>"
    }
  ]
}
'

{
  "knowledgeBaseId": "<string>",
  "name": "<string>",
  "description": "<string>",
  "sources": [
    {
      "source_id": "<string>",
      "source_type": "<string>",
      "filename": "<string>"
    }
  ],
  "workspaceId": 123
}