DynamicSupervisor and Ecto.Adapters.SQL.Sandbox problem

[joey_the_snake]

@al2o3cr

A general note: changing the sandbox mode affects what happens when you call checkout, so these should likely be in the opposite order.

For shared mode the checkout actually has to happen first. The checkout requests go through a GenServer which will have its state set with the owner’s connection when changing the mode to shared.