Custom handle

[tnakamot]

See this comment about the request to deal with custom handles:
#1 (comment)

For example, LSST DocuShare has a custom handle 'presentation-xxxx'
https://docushare.lsstcorp.org/docushare/dsweb/View/Collection-343

The idea to treat unknown handle as DocumentObject seems to be plausible, but I still want to have some error checks of handle names for my use. In particular, I would like to get a proper error message for typos in a handle name. For example, if the handle name is 'Documen-xxxx', I would like this library to say 'this is an invalid handle' rather than trying to access the DocuShare site.

Will think about it.