Add choose type of file before upload

Now the user must choose between the DP Multi User and Batch jobs with respective keys: dp_multiuser and batch_jobs, the expected response for:

1. DP Multi User will be:

{
  "name": "Report_20250324.xlsx",
  "content": "base64EncodedString1"
} 

2. Batch jobs will be:

{
  "file1": {
    "name": "Processed_Report.xlsx",
    "content": "base64EncodedString1"
  },
  "file2": {
    "name": "Summary_Report.xlsx",
    "content": "base64EncodedString2"
  }
}