fix(entity-import): pass validated input to payload field

[m90]

I noticed the payload of a WikiEntityImport model (which is saved for debugging purposes) will currently end up as null:

      App\WikiEntityImport {#6869                                                                                                                                                                           
        +id: 1,
        +created_at: "2024-07-31 11:56:59",
        +updated_at: "2024-07-31 11:57:43",
        +wiki_id: 413,
        status: "success",
        started_at: "2024-07-31 11:56:59",
        finished_at: "2024-07-31 11:57:43",
        +payload: null,
      },