OpenTelemetry authentication

[sonOfRa]

While #40 adds support for OpenTelemetry-based tracing, for now all 3 interaction points lack authentication:

• Jaeger UI
• Jaeger collector endpoint
• OpenTelemetry collector endpoint

The Jaeger UI cannot be secured on its own, but this is easily doable via any HTTP reverse proxy that supports OIDC.
The collector endpoints.

The Jaeger collection endpoint also does not support authentication out of the box, but there are some blog posts by the developers that outline how it could be done: https://medium.com/jaegertracing/protecting-the-collection-of-spans-1948d88682e5

The OTEL collector endpoint supports OIDC out of the box: https://opentelemetry.io/docs/collector/configuration/#authentication, but the agent does not. It looks like the suggested way of doing things is having the collector on localhost (or a sidecar) of the application, where only the application can talk to the collector. The collector then forwards them to Jaeger. This whole setup needs some proper investigation to see how and if it all works.