Handle more errors by logging them

[code-cro]

Do error handing for Tcp connection.

jsonrpc_v2_client/src/lib.rs

Line 134 in 435e8e3

let mut client = TcpStream::connect(&service_address.url).await.unwrap();

Do error handling when serializing Request object with to_string_pretty method.

jsonrpc_v2_client/src/lib.rs

Line 137 in 435e8e3

let json = serde_json::to_string_pretty(&self).unwrap();