Enhancement to "file" display to group resources

[LynnMcRae]

Note that this ticket is about File objects only, those with content-type=file, NOT about file resources mixed in with other content-types, like an Image or Media object with added resources of type=file. We generally refer to those as "mixed content".

The DOR content model has files contained in a that provides added description. Multiple files that shared some level of identity can be placed together in a . Sometimes, as in a master/derivative case, only one might be published, but we have cases where multiple files from one resource are indeed visible. When this happens, the grouping should be visible to the user with the label shown once for a set of files.

The current presentation for File objects is a simple list where all files from all resources are presented linearly at the same level, ignoring whether files are grouped together as part of one . To date, the implications of this have been somewhat innocuous as in this example (https://purl.stanford.edu/bc006dj2846, which will someday be a media object but is currently described as a File object):

The pairing of files can be inferred from the repeated label, but it's not immediately apparent that the "4 items" is a 2+2. The situation worsens when there is more grouping of greater significance. Note this example -- https://purl.stanford.edu/zx935qw7203 (a work-in-progress at the time of this ticket).

and

Very large dataset files are being split for download. When finished, this object will have 19 resources containing 8-12 related files each. It will be critical that the grouping be apparent, perhaps under some user control, e.g., expand/collapse. The hope here is to use an extended label to convey information about the grouping with a link to help for download and assembly.