Add Opentelemetry module

[vladpaiu]

Summary
Add Opentelemetry module tracing the OpenSIPS routes execution and the logs they produce

Details
Opentelemetry is providing a standardized, vendor-neutral framework (APIs, SDKs, tools) to collect, process, and export telemetry data (traces, metrics, logs) from distributed systems, enabling deep insights into application performance, faster debugging, and preventing vendor lock-in by routing data to multiple observability backends.

Solution
Each new message processing produce a new root span ( with the full SIP message attached to it ), and then a new child span is added for each route execution the SIP message goes through. A new log_level parameter is introduced to the opentelemetry module, and logs will be attached to the respective child span.

The module also supports async & resume route script jumping ( maintaining the parent span and the total execution duration ) so you can get a clear view of the full script execution even when using async().

Compatibility
New module, no backwards compatibility issues

Future Notes
We can later integrate the metrics part by exporting a list of statistics as well to the otel spans ( similar to prometheus ), as well as attaching a list of AVPs to the spans, to get a better idea of the 'route code path' that the SIP messages are taking

Examples

Testing with

route {
...
        if (is_method("REGISTER")) {
                # store the registration and generate a SIP reply
                route(handle_register);
                exit;
        }
 ....
 }
 
 route[handle_register] {
        xlog("Received $rm now for $ci , sleeping now \n");
        async(sleep(1),"RESUME_SLEEP");
}

route[RESUME_SLEEP] {
        xlog("Resumed from sleep, calling save $ci \n");
        route(SAVE_REGISTER);

}

route[SAVE_REGISTER] {
        xlog("Saving $rm now for $ci \n");
        if (!save("location"))
                xlog("failed to register AoR $tu\n");
        exit;
}

an opentelemetry reader produces the following spans showing the 1s execution duration through the full script execution path ( with script lines numbers attached as tags )

with the logs attached to the respective route child spans