It seems that the "wallet" parameter is not recognized by the "load_wallet" method in the context of the JSON-RPC call you are making.
One solution could be to pass the wallet path as a command-line argument when starting the JSON-RPC server. For example, if you are using Electrum, you could start the server with the following command:
electrum --testnet --rpcuser=<username> --rpcpassword=<password> --rpchost=localhost --rpcport=8000 /electrum/testnet/wallets/orders001
This command starts the Electrum server in testnet mode and specifies the wallet path as the last argument.
Once the server is running, you can make JSON-RPC requests to it without including the "wallet" parameter in the payload. The server should automatically load the wallet specified in the command-line argument.
Alternatively, you could try using the "load_wallet_file" method instead of "load_wallet". According to the Electrum documentation, "load_wallet_file" takes a single argument, which is the path to the wallet file. Here is an example payload:
Note that the wallet path is passed as an array element in the "params" field, not as a separate "wallet" parameter.