ParseAsTMIDOrFetchName parses idOrName as model.TMID.

RelAttachmentsDir is a helper function which calculates the relative path of the attachments directory for given attachment container.

AttachmentContainerRef contains a reference to an entity which can have file attachments Either TMName field must be not empty, or TMID.

ThingModel is a model for unmarshalling a Thing Model to be imported.