Function to approve ERC20 token transfer using eth_sendTransaction.

TODO: implement pagination.

TODO: de-duplicate http handling.

osmosis and solana has wallet issues.

TODO: make it configurable for different environments.

ERC20ApproveABI is the ERC20 function signature for "approve(address,uint256)".

TODO: get this mapping dynamically at app start and cache it okto supports only a sub set of networks returned by /supported-networks.

TODO: use okto /aupported_tokens and /supported_networks api's do not hardcode networks and tokens for now, all networks returnd by /supported_networks do not work.

these values are from lifi supported tokens api.

see the okto supported tokens and supported networks these values are from okto supported tokens api.

TODO: de-duplicate response struct.

TODO: the portfolio response structure is different from whats docuemnted.