Add auto-configuration for OTLP gRPC format

[mhalbritter]

Implement auto-configuration for OpenTelemetry's OtlpGrpcSpanExporter.

          Well, since the endpoint URL has to be provided now, it can be used to figure out which type of exporter the user wants to configure and also support the gRPC option.

Originally posted by @vpavic in #35596 (comment)

[meisten]

Maybe it will be useful to someone. Until autoconfiguration is implemented out-of-the-box, you can use this code in your project.

package org.example.infrastructure.monitoring;

import io.opentelemetry.exporter.otlp.trace.OtlpGrpcSpanExporter;
import org.springframework.boot.actuate.autoconfigure.tracing.otlp.OtlpProperties;
import org.springframework.boot.actuate.autoconfigure.tracing.otlp.OtlpTracingConnectionDetails;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
class OtlpGrpcExporterAutoConfiguration {

    /**
     * This is a copy of autoconfiguration {@link io.opentelemetry.exporter.otlp.http.trace.OtlpHttpSpanExporter} from
     * {@link org.springframework.boot.actuate.autoconfigure.tracing.otlp.OtlpTracingConfigurations}, but for gRPC.
     */
    @Bean
    OtlpGrpcSpanExporter otlpGrpcSpanExporter(OtlpProperties properties, OtlpTracingConnectionDetails connectionDetails) {
        var builder = OtlpGrpcSpanExporter.builder()
                                          .setEndpoint(connectionDetails.getUrl())
                                          .setTimeout(properties.getTimeout())
                                          // TODO: use Enum#name instead of String#valueof. OtlpProperties#Compression
                                          //  enum has package private access
                                          .setCompression(String.valueOf(properties.getCompression()).toLowerCase());

        properties.getHeaders().forEach(builder::addHeader);
        return builder.build();
    }

}

application.yml:

management:
  otlp:
    tracing:
      endpoint: http://localhost:4317/v1/traces
      compression: gzip

[timpeeters]

I've provided an initial proposal to support OtlpGrpcSpanExporter.
See #41213
Looking forward to any feedback.

[mhalbritter]

Superseded by #41213.