Authenticator interface can't be used with OtlpHttpSpanExporter

[GerardPaligot]

Describe the bug
We can't use the Authenticator interface to configure http client used by OtlpHttpSpanExporter. You can only use Authenticator interface with OkHttpExporterBuilder which is used internally by the span exporter.

Steps to reproduce

val exporter: OtlpHttpSpanExporter =
    OtlpHttpSpanExporter.builder()
        .setEndpoint("http://localhost:4318/v1/traces")
        .build()
Authenticator.setAuthenticatorOnDelegate(exporter, Authenticator {
    return@Authenticator mapOf(
        "Authorization" to "Bearer <token>"
    )
})

Caused by: java.lang.IllegalArgumentException: Delegate field is not type DefaultGrpcExporterBuilder or OkHttpGrpcExporterBuilder.
    at io.opentelemetry.exporter.internal.auth.Authenticator.setAuthenticatorOnDelegate(Authenticator.java:48)

What did you expect to see?
It should be possible to configure an authentication interceptor / delegate to generate a valid token when it is necessary

What version and what artifacts are you using?
Artifacts: opentelemetry-api, opentelemetry-sdk, opentelemetry-exporter-otlp, opentelemetry-exporter-common
Version: 1.25.0

Environment
Compiler: zulu JDK 17
OS: macOS 13.3.1

[jack-berg]

I've verified authenticator and Authenticator.setAuthenticatorOnDelegate are working as expected. Added an additional test case in #5391 to be sure.

I see in your repro you are trying to set the authenticator on the exporter instead of on the exporter builder. Try this instead:

val exporterBuilder: OtlpHttpSpanExporterBuilder =
    OtlpHttpSpanExporter.builder()
        .setEndpoint("http://localhost:4318/v1/traces")
Authenticator.setAuthenticatorOnDelegate(exporterBuilder, Authenticator {
    return@Authenticator mapOf(
        "Authorization" to "Bearer <token>"
    )
})

[jack-berg]

Closing as #5391 indicates that the API is working as expected.