Sandbox-Only Endpoint List:
- POST accounts Create an account on the sandbox
- POST accounts/:account_id/features Add an account feature to an account on the sandbox
- POST accounts/:account_id/funding_instruments Add a funding instrument to an account on the sandbox
- DELETE accounts/:account_id Delete an account on the sandbox
- DELETE accounts/:account_id/features Delete an account feature from an account on the sandbox
- DELETE accounts/:account_id/funding_instruments/:funding_instrument_id Delete a funding instrument from an account on the sandbox