This PR adds custom /txs endpoint, which is removed in cosmos-sdk v0.44
{
"tx": StdTx,
"mode": "block" | "sync" | "async",
// Below fields are newly introduced optional arguments.
// To convert legacy tx to new proto tx, we need each signer's sequence number.
// If this field is not given, we fetch the sequence from the chain state. Normal
// users can skip this field as well, but the users who are sending faster than block
// time need to provide this field.
"sequences": ["1", "2"],
"fee_granter": "",
"timeout_height": "10"
}