Additional filters for `GET#Refunds` endpoint

Changes implemented:

Add `updated_at` field for Refunds object

Add updated_at field for Refunds object displayed in CoinGate V2 API endpoints

added

GET Outgoing Fees API endpoint

Added new API endpoint to List Outgoing Fees:

added

Order Blockchain Transactions API

Added new API endpoints to get Order Blockchain Transactions:

improved

JSON Payment Callback Format

Now allows to change Payment Callback format to JSON. If you want to set for currently used API APP, login to your account dashboard, go to Merchant -> API -> Apps and click Edit.

added

Ledger Transactions API Endpoints

Added new API endpoints to get ledger transactions:

improved

Fees in Payment Callback

Added fees parameter in Payment Callback