Changes to Get Balance Info

added the non-success response with the status 409

added the optional property next_payment_date to the response with the 200 status

response property current_balance_pence deprecated

response property minimum_withdrawal_threshold_pence deprecated

response property total_earnings_pence deprecated

added the required property current_balance to the response with the 200 status

added the required property minimum_withdrawal_threshold to the response with the 200 status

added the required property total_earnings to the response with the 200 status