describing and endpoint for uploading file(s)

/attachments:
  summary: upload an attachment
  post:
    requestBody:
      content:
        multipart/form-data:
          schema:
            type: object
            properties:
              file:
                type: string
                format: binary
    responses:
      204:
        description: successfully created attachment

/attachments:
  summary: upload multiple attachments
  post:
    requestBody:
      content:
        multipart/form-data:
          schema:
            type: object
            properties:
              files:
                type: array
                items:
                  type: string
                  format: binary
    responses:
      204:
        description: successfully created attachment