OptionalartifactFor source='artifact': the underlying MJArtifact.ID so clicks can open the viewer.
OptionalartifactFor source='artifact': resolved MJArtifactType.Name, e.g. "Data Snapshot". Drives the type badge.
OptionalartifactFor source='artifact': the underlying MJArtifactVersion.ID.
OptionalcontentOptionalheightOptionalsourceSource of the attachment: 'upload' for chat uploads, 'artifact' for artifact picker
OptionalthumbnailOptionalwidth
Represents an attachment on a message for display