Fix: default to application/json content-type.
Fix: default to application/json content-type.

sweir27/doppler,sweir27/doppler,dblock/doppler,artsy/doppler,mzikherman/doppler,artsy/doppler,mzikherman/doppler,artsy/doppler,dblock/doppler,artsy/doppler,dblock/doppler,sweir27/doppler,mzikherman/doppler