SAW to DEX transition

[cbeaulaurier]

Sprout was originally identified as an early adopter, however the DEX project is experiencing some delays. Sprout now has the choice to be an early adopter or not.

We plan to wait for an important feature before we adopt DEX: automated user migration.
Without this, our users will have to manually match their accounts, which was by far the most disruptive part of the SAW launch. Helping people who have mismatched their SAW and Sprout accounts is a significant part of our user support, indicating that this is a very common pain point.

[keithligon]

pr for initial config: https://github.com/cssat/sprout/pull/256