This is purely the source code of the rust end of opentelemetry. It does
not have build tooling wired up yet, nor is this used from the C code.

Signed-off-by: Ava Hahn <a.hahn@f5.com>
Signed-off-by: Gabor Javorszky <g.javorszky@f5.com>

Co-authored-by: Ava Hahn <a.hahn@f5.com>

Adds the --otel flag to the configure command and the various build time
variables and checks that are needed in this flow.

It also includes the nxt_otel.c and nxt_otel.h files that are needed for
the rest of Unit to talk to the compiled static library that's generated
from the rust crate.

Signed-off-by: Ava Hahn <a.hahn@f5.com>
Signed-off-by: Gabor Javorszky <g.javorszky@f5.com>

Co-authored-by: Ava Hahn <a.hahn@f5.com>

Enables Unit to parse the tracestate and traceparent headers and add it
to the list, as well as calls to nxt_otel_test_and_call_state.

Signed-off-by: Ava Hahn <a.hahn@f5.com>

Adds code responsible for users to apply the `telemetry` configuration
options.

configuration snippet as follows:
{
    "settings": {
        "telemetry": {
            "batch_size": 20,
            "endpoint": "http://lgtm:4318/v1/traces",
            "protocol": "http",
            "sampling_ratio": 1
        }
    },
    "listeners": {
        "*:80": {
            "pass": "routes"
        }
    },
    "routes": [
        {
            "match": {
                "headers": {
                    "accept": "*text/html*"
                }
            },
            "action": {
                "share": "/usr/share/unit/welcome/welcome.html"
            }
        },
        {
            "action": {
                "share": "/usr/share/unit/welcome/welcome.md"
            }
        }
    ]
}

Signed-off-by: Ava Hahn <a.hahn@f5.com>
Signed-off-by: Gabor Javorszky <g.javorszky@f5.com>

Co-authored-by: Ava Hahn <a.hahn@f5.com>

Tiny bracket balance fix.

Signed-off-by: Ava Hahn <a.hahn@f5.com>
Signed-off-by: Gabor Javorszky <g.javorszky@f5.com>

These changes are generated by the openapi generator through a make
command.

Signed-off-by: Ava Hahn <a.hahn@f5.com>
Signed-off-by: Gabor Javorszky <g.javorszky@f5.com>