The standard order execution flow assumes that the executor must be the resolver address specified in the order structure. While this is important for security, it also creates certain restrictions for resolvers since it eliminates the possibility of indirectly calling the order execution method, for example, from custom smart contacts.
For this purpose, the Trusted Forwarders mechanism (EIP-2771) was implemented in Flash Trade.
The KinetexForwarder contract is an ERC2771Forwarder implementation based on the OpenZeppelin library. It extends signature-recovery options to allow both meta transactions from externally owned accounts (EOAs) and ERC-1271 signatures from smart contract via the SignatureChecker library implemented by OpenZeppelin.
Some of the main Kinetex Flash contracts inherit OpenZeppelin's ERC2771Context, which allows meta transactions from constructor-initialized trusted forwarder contract addresses. The KinetexForwarder contract will be deployed and used as the trusted forwarder in these contexts.