Add support for traking original/physical document

[ciur]

Feature request from reddit comment

Add support for "tracking" the original/physical (like the scanned physical copy) version of a document in some manner. E.g. could a document archived in papermerge have a tag or some structured (searchable?) info like "has original stored under Cabin A/Folder B" or similar.

Remarks: feature described here plays great with upcoming metadata feature. User can add e.g. four metadata text fields each describing part of physical location:

• text field 1: room number: e.g. R11
• text field 2: shelf number: e.g. S72
• text field 3: row number: R6
• text field 4: row position: P3

Thus, each document may have attached following metadata field like: R11 S6 R6 P1, R11 S6 R3 P2 describing path to physical location of the document. Of course metadata would be searchable via full text search.