URN format for hash

[bjuergens]

current format looks like this v1-sha256-128M-aa669dcefba57e01bd7ff0526a0001d2118f06adc8106d265b5743b0ee90084f

But there are already formats for hashed trees

• https://www.w3.org/TR/uri-clarification/#
• https://www.rfc-editor.org/rfc/rfc8141.txt
• https://en.wikipedia.org/wiki/Magnet_URI_scheme#URN,_containing_hash_(xt)
• https://en.wikipedia.org/wiki/Uniform_Resource_Name

(Till showed me a specific one, but I forgot)

problem: might not be compatible with hadoop fs

solution: replace ":" with "-", and maybe "-" with "--" (assuming "-" can be part of the URN in the first place)