Unfurled media item used by thumbnail, media gallery and file components.
| Property | Type | Description |
|---|---|---|
| attachment_id | String | The id of the uploaded attachment (response only) |
| content_type | String | The media type of the content (response only) |
| height | Integer | The height of the media item (response only) |
| proxy_url | String | The proxied url of the media item (response only) |
| url | String | Supports arbitrary urls and attachment://<filename> references |
| width | Integer | The width of the media item (response only) |