Upload document to knowledge base

curl --request POST \
  --url https://api.wacht.dev/ai/knowledge-bases/{kb_id}/documents \
  --header 'Authorization: <api-key>' \
  --header 'Content-Type: multipart/form-data' \
  --form file='@example-file' \
  --form 'title=Product Manual' \
  --form 'description=Complete product manual for users'

{
  "id": "1234567890123456789",
  "created_at": "2024-01-15T10:30:00Z",
  "updated_at": "2024-01-15T10:30:00Z",
  "title": "Product Manual",
  "description": "Complete product manual for users",
  "file_name": "product_manual.pdf",
  "file_size": 1048576,
  "file_type": "application/pdf",
  "file_url": "https://s3.amazonaws.com/bucket/path/to/file.pdf",
  "knowledge_base_id": "9876543210987654321",
  "processing_metadata": {}
}