Upload customer document

Uploads a KYC (Know Your Customer) document for a customer to the specified Payment Service Provider (PSP). **Request body:** | Field | Type | Required | Description | | --- | --- | --- | --- | | `pspId` | string | Yes | Identifier of the payment provider (e.g., `Finmo`) | | `fileName` | string | No | Name of the file being uploaded (e.g., `passport.jpg`) | | `fileType` | string | Yes | MIME type of the file. Only supports:• `image/png`• `image/jpeg`• `image/jpg`• `application/pdf` | | `description` | string | No | A short description of the document (e.g., `Passport front`) | | `base64` | string | Yes | Base64-encoded file content | Response Body: 200 OK | **Field** | **Type** | | --- | --- | | documentId | string | | documentType | string | | fileName | string | | fileType | string | | description | string | 400 BAD REQUEST - 403 FORBIDDEN - 401 UNAUTHORIZED - 500 INTERNAL ERROR | **Field** | type | | --- | --- | | timestamp | date(yyyy-MM-dd'T'HH:mm:ss.SSS'Z') | | title | string | | type | string | | status | number | | soaCode | string | | detail | string |