use base 36 values of context ids for scribd_user
use base 36 values of context ids for scribd_user

this will allow for 46k shards and 60 million
documents per context type and remain under 10
digits for scribd. scribd_user format is
first_letter or context_type, shard_id in hex,
'-', and context_id in base 36.
Submission 21438841 on Shard 13456 = "sads-cribd"

fixes CNVS-10238

test plan
 - in production create upload a scribdable document
 - document should render

Change-Id: Iab226c25835e6779928464a0ea0ac4b91c9cc6a2
Reviewed-on: https://gerrit.instructure.com/28057
Reviewed-by: Cody Cutrer <c4fe2b1d90ef8f2548c8aeabfa633434316f0305@instructure.com>
Tested-by: Jenkins <d95b56ce41a2e1ac4cecdd398defd7414407cc08@instructure.com>
Product-Review: Rob Orton <7e09c9d3e96378bf549fc283fd6e1e5b7014cc33@instructure.com>
QA-Review: Rob Orton <7e09c9d3e96378bf549fc283fd6e1e5b7014cc33@instructure.com>

juoni/canvas-lms,Unow/canvas-lms,wrdsb/canvas-lms,skmezanul/canvas-lms,djbender/canvas-lms,tgroshon/canvas-lms,grahamb/canvas-lms,kyroskoh/canvas-lms,whalejasmine/canvas-lms,skmezanul/canvas-lms,Jyaasa/canvas-lms,sfu/canvas-lms,redconfetti/canvas-lms,samuels410/greatlakes-lms,utkarshx/canvas-lms,Jyaasa/canvas-lms,samuels410/greatlakes-lms,whalejasmine/canvas-lms,wye0220/shindig-canvas,va7map/canvas-lms,kyroskoh/canvas-lms,venturehive/canvas-lms,redconfetti/canvas-lms,efrj/canvas-lms,arrivu/arrivu-lms,usmschuck/canvas,va7map/canvas-lms,djbender/canvas-lms,leftplusrightllc/canvas-lms,efrj/canvas-lms,antoniuslin/canvas-lms,wrdsb/canvas-lms,landonwilkins/canvas-lms,kyroskoh/canvas-lms,efrj/canvas-lms,utkarshx/canvas-lms,whalejasmine/canvas-lms,utkarshx/canvas-lms,venturehive/canvas-lms,greyhwndz/canvas-lms,Rvor/canvas-lms,arrivu/arrivu-lms,antoniuslin/canvas-lms,leftplusrightllc/canvas-lms,sdeleon28/canvas-lms,Unow/canvas-lms,arrivu/qibla-ecampus,redconfetti/canvas-lms,Rvor/canvas-lms,djbender/canvas-lms,landonwilkins/canvas-lms,greyhwndz/canvas-lms,arrivu/hoodemo,fronteerio/canvas-lms,ShreniiNepal/shrenii_lmp,SwinburneOnline/canvas-lms,roxolan/canvas-lms,sdeleon28/canvas-lms,shidao-fm/canvas-lms,grahamb/canvas-lms,arrivu/arrivu-lms,roxolan/canvas-lms,wye0220/shindig-canvas,grahamb/canvas-lms,ShreniiNepal/shrenii_lmp,landonwilkins/canvas-lms,SwinburneOnline/canvas-lms,ShreniiNepal/shrenii_lmp,efrj/canvas-lms,sdeleon28/canvas-lms,sfu/canvas-lms,samuels410/greatlakes-lms,Rvor/canvas-lms,jay3126/canvas-lms,fronteerio/canvas-lms,leftplusrightllc/canvas-lms,fronteerio/canvas-lms,samuels410/greatlakes-lms,skmezanul/canvas-lms,grahamb/canvas-lms,venturehive/canvas-lms,kyroskoh/canvas-lms,juoni/canvas-lms,tgroshon/canvas-lms,HotChalk/canvas-lms,antoniuslin/canvas-lms,sfu/canvas-lms,usmschuck/canvas,Unow/canvas-lms,SwinburneOnline/canvas-lms,landonwilkins/canvas-lms,skmezanul/canvas-lms,wye0220/shindig-canvas,grahamb/canvas-lms,HotChalk/canvas-lms,sfu/canvas-lms,wrdsb/canvas-lms,utkarshx/canvas-lms,juoni/canvas-lms,jay3126/canvas-lms,jay3126/canvas-lms,sfu/canvas-lms,redconfetti/canvas-lms,arrivu/qibla-ecampus,tgroshon/canvas-lms,shidao-fm/canvas-lms,ShreniiNepal/shrenii_lmp,HotChalk/canvas-lms,SwinburneOnline/canvas-lms,jay3126/canvas-lms,usmschuck/canvas,sfu/canvas-lms,fronteerio/canvas-lms,djbender/canvas-lms,wrdsb/canvas-lms,sfu/canvas-lms,leftplusrightllc/canvas-lms,Rvor/canvas-lms,HotChalk/canvas-lms,greyhwndz/canvas-lms,va7map/canvas-lms,roxolan/canvas-lms,roxolan/canvas-lms,whalejasmine/canvas-lms,greyhwndz/canvas-lms,arrivu/hoodemo,tgroshon/canvas-lms,va7map/canvas-lms,antoniuslin/canvas-lms,usmschuck/canvas,juoni/canvas-lms,shidao-fm/canvas-lms,venturehive/canvas-lms,Jyaasa/canvas-lms,sdeleon28/canvas-lms,Jyaasa/canvas-lms,arrivu/qibla-ecampus,shidao-fm/canvas-lms,arrivu/hoodemo