fix delete, will not remove the graph from virtuoso if the prefix is different from default

[manonthegithub]

[manonthegithub]

one problem…. with the prefix now it is possible to create several graphs for one file… so when you delete the second one, the file wont be there and will for now throw 500 i think… what should we actually do? or we should check if the file already exists and not create the second graph?

[manonthegithub]

@kurzum

[manonthegithub]

@kurzum we can also make different paths for files with different graphids/prefixes (upon saving)... but need to think about how should these paths look like

[kurzum]

@manonthegithub I would document this in swagger:
document in swagger:

1. explain prefix better in graph/save and its behaviour and also what is used as default.
2. TBD I think that the prefix parameter should be transparent, and users should do as they wish. So there are wrong usage, e.g. "http://example.org" leads to "http://example.orgjanni/testing/group" and "http://example.org//" leads to "http://example.org//janni/testing/group" but also they can do "http://example.org/additionalpath/" or whatever. This way they could also use / as relative path, so it is more flexible, but user can mess up more, but this is always the case with flexibility....
3. document the current pitfall with delete, i.e. if you write a graph with prefix and delete without prefix OR upload same file with different prefixes.

[manonthegithub]

@kurzum as an option we can calculate a hash of prefix and then save the file on disk using hash as path segment
/....
WDYT?