Include values in log messages

[sgoll]

Description

This makes sure to include values when printing out log messages. This is done by passing the format string with variadic arguments to vsnprintf() to handle all the formatting.

Fixes #22

[sgoll]

FYI, this is being blocked by HMIProject/open62541-sys#9 for proper vsnprintf() support on Microsoft Windows.

[sgoll]

You can test the output with RUST_LOG=debug cargo run --example async_client.

[uklotzde]

By enclosing the invocations of printf() in a loop the code might become more compact and the closure would not be needed. But let's leave it as is. Works and the code is readable.

[uklotzde]

Ouch:

[2024-01-19T13:05:49Z WARN  open62541::client] AcceptAll Certificate Verification. Any remote certificate will be accepted.
[2024-01-19T13:05:49Z INFO  open62541::client] Connecting to endpoint opc.tcp://localhost:4840/OPC_UA_Server
thread 'tokio-runtime-worker' panicked at /home/uk/.cargo/git/checkouts/open62541-bd40fc1209456320/697e248/src/client.rs:274:9:
assertion failed: msg_length + 1 >= msg_buffer.len()
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

[uklotzde]

The loop would ensure that the code paths are shared to prevent one-off errors like this.

[sgoll]

@uklotzde Interesting. Can you send me a reproduction? I tested the edge cases and saw no such error on my system. Can the implementations of vsnprintf() differ in what return value they produce?

Cont'd in #29