# Upload transaction attachment

Upload an attachment for a transaction

Endpoint: POST /transactions/{transactionId}/attachment
Version: 1.0.0
Security: ApiKeyAuth

## Path parameters:

  - `transactionId` (string, required)
    Transaction identifier
    Example: "txn-abc-123"

## Request fields (multipart/form-data):

  - `file` (string, required)
    Attachment file

## Response 201 fields (application/json):

  - `id` (string, required)
    File identifier (DigitalOcean Spaces object key)
    Example: "files/2024/03/budget-report.pdf"

  - `name` (string, required)
    Original filename
    Example: "call-sheet-day-3.pdf"

  - `type` (string, required)
    MIME type
    Example: "application/pdf"

  - `size` (integer, required)
    File size in bytes
    Example: 1048576

## Response 400 fields (application/json):

  - `error` (string, required)
    Error message
    Example: "Invalid request parameters"

  - `details` (object)
    Additional error details
    Example: {"field":"projectId","reason":"Project not found"}

  - `code` (string)
    Error code
    Example: "VALIDATION_ERROR"

## Response 401 fields (application/json):

  - `error` (string, required)
    Error message
    Example: "Invalid request parameters"

  - `details` (object)
    Additional error details
    Example: {"field":"projectId","reason":"Project not found"}

  - `code` (string)
    Error code
    Example: "VALIDATION_ERROR"

## Response 404 fields (application/json):

  - `error` (string, required)
    Error message
    Example: "Invalid request parameters"

  - `details` (object)
    Additional error details
    Example: {"field":"projectId","reason":"Project not found"}

  - `code` (string)
    Error code
    Example: "VALIDATION_ERROR"

## Response 500 fields (application/json):

  - `error` (string, required)
    Error message
    Example: "Invalid request parameters"

  - `details` (object)
    Additional error details
    Example: {"field":"projectId","reason":"Project not found"}

  - `code` (string)
    Error code
    Example: "VALIDATION_ERROR"