Request to expose string based configuration in autoprop module.

[pavankrish123]

Background

Currently autoprop module only supports setting the propagator either by passing actual propagators objects or via environment variable OTEL_PROPAGATOR.

This limits consumers of the module to expose these settings as external configuration strings.

For example OTel Collector using this autoprop can only configure the autoprop module either by introducing

1. it's own configuration semantics and later convert the configuration strings into propagator objects to pass them to the autoprop or

2. Set the environment variables from withing the process by taking the values as configuration strings.

But having an api that takes in a string with values equivalent to what gets passed in OTEL_PROPAGATOR let consumers expose the sdks settings as configuration.

see open-telemetry/opentelemetry-collector#5572

[MrAlias]

Would adding a function like the following accomplish this request?

// RetrieveTextMapPropagator returns a TextMapPropagator composed from the passed names.
// Each name must match an already registered TextMapPropagator (see the RegisterTextMapPropagator function for more information), or a default (tracecontext, baggage, b3, b3multi, jaeger, xray, or ottrace).
//
// If "none" is passed, or no names are provided, the returned TextMapPropagator will be a no-operation implementation.
//
// An error is returned for any un-registered names.
// The remaining, known, names will be used to compose a TextMapPropagator that is returned with the error.
func RetrieveTextMapPropagator(names ...string) (propagation.TextMapPropagator, error) {
	/* implementation */
}

[pavankrish123]

Yes the api would do just fine. Thank you.