Add Flash Bookmark

curl --request POST \
  --url http://localhost:3000/api/flash/bookmarks/add \
  --header 'Content-Type: application/json' \
  --data '
{
  "flashId": "<string>",
  "artistId": "<string>",
  "notes": "<string>",
  "customTags": [
    "<string>"
  ]
}
'

{
  "success": true,
  "bookmark": {
    "id": "<string>",
    "userId": "<string>",
    "flashId": "<string>",
    "artistId": "<string>",
    "createdAt": 123,
    "notes": "<string>",
    "customTags": [
      "<string>"
    ]
  }
}