JSON API Methods

Developers want to use native object types within their app's view and controller layers and do not want to use Couchbase Lite document types directly within their view layers.

Edit 

PRD: https://docs.google.com/document/d/103CYes0UQJ7y9-qtsy-vK8_Uziw_TdF-imhRBrNeOF8/edit# (partial)

API: https://docs.google.com/document/d/1H0mnutn-XXIADvGT_EjINAOVwt0Ea8vwW70v0i_PO54/edit?ts=60369f6e#heading=h.pp69qv5xq2la

Document the JSON API changes for blobs, docs etc.