Bug 1239428 - Docs: Clarify process for API credential approval
Bug 1239428 - Docs: Clarify process for API credential approval

* Recommend using the same `client_id` for stage/prod.
* Mention the need to file a bug (and where) for requesting approval.
* Explain prod approval needs submission to be working on stage first.

kapy2010/treeherder,akhileshpillai/treeherder,KWierso/treeherder,glenn124f/treeherder,edmorley/treeherder,tojonmz/treeherder,tojon/treeherder,tojonmz/treeherder,wlach/treeherder,edmorley/treeherder,KWierso/treeherder,kapy2010/treeherder,tojonmz/treeherder,tojon/treeherder,KWierso/treeherder,kapy2010/treeherder,wlach/treeherder,tojon/treeherder,akhileshpillai/treeherder,akhileshpillai/treeherder,tojon/treeherder,akhileshpillai/treeherder,tojonmz/treeherder,glenn124f/treeherder,tojonmz/treeherder,akhileshpillai/treeherder,wlach/treeherder,kapy2010/treeherder,glenn124f/treeherder,glenn124f/treeherder,glenn124f/treeherder,tojonmz/treeherder,wlach/treeherder,edmorley/treeherder,wlach/treeherder,KWierso/treeherder,edmorley/treeherder,akhileshpillai/treeherder,kapy2010/treeherder,glenn124f/treeherder,wlach/treeherder