enable usage of custom Exporters using environment variable OTEL_TRACES_EXPORTER

[shadow0wolf]

I have implemented a custom exporter , i intend configure otel instrumented application to use this exporter without explicitly implementing AutoConfigurationCustomizerProvider and make otel instrumentation use it through "OTEL_TRACES_EXPORTER" environment variable.

[jkwatson]

I believe if you implement the io.opentelemetry.sdk.autoconfigure.spi.traces.ConfigurableSpanExporterProvider SPI interface, and make sure your custom exporter is on the classpath, then you can use whatever is returned from the getName() method in your env var and it should work.