Implement ExtendedTextMapGetter in instrumentations

[jamesmoessis]

Is your feature request related to a problem? Please describe.

Spec has recently changed to specify extraction of multiple values for a given key: open-telemetry/opentelemetry-specification#4295

The Java SDK has added ExtendedTextMapGetter to handle this: open-telemetry/opentelemetry-java#6852 (when stabilised this extension may become a default method on TextMapGetter which should be then implemented by instrumentations).

Describe the solution you'd like

For instrumentations that have carriers that support multiple values for a single key (most HTTP implementations) this should be a relatively straightforward change.

It does not necessarily need to be supported by all instrumentations.

[xiepuhuan]

I have gone through all the instrumentations and found that the following 15 TextMapGetter need to be modified. Can I make all the changes to TextMapGetter in single PR?
@trask

• io.opentelemetry.instrumentation.grpc.v1_6.GrpcRequestGetter
• io.opentelemetry.javaagent.instrumentation.grizzly.HttpRequestHeadersGetter
• io.opentelemetry.instrumentation.spring.webmvc.v6_0.JakartaHttpServletRequestGetter
• io.opentelemetry.instrumentation.spring.webmvc.v5_3.JavaxHttpServletRequestGetter
• io.opentelemetry.javaagent.instrumentation.jetty.v12_0.Jetty12TextMapGetter
• io.opentelemetry.instrumentation.kafka.internal.KafkaConsumerRecordGetter
• io.opentelemetry.javaagent.instrumentation.liberty.dispatcher.LibertyDispatcherRequestGetter
• io.opentelemetry.instrumentation.awssdk.v2_2.internal.SqsParentContext.MessageAttributeValueMapGetter
• io.opentelemetry.javaagent.instrumentation.netty.v3_8.server.NettyHeadersGetter
• io.opentelemetry.instrumentation.ratpack.v1_7.internal.RatpackGetter
• io.opentelemetry.instrumentation.restlet.v1_1.internal.RestletHeadersGetter
• io.opentelemetry.instrumentation.restlet.v2_0.internal.RestletHeadersGetter
• io.opentelemetry.javaagent.instrumentation.servlet.ServletRequestGetter
• io.opentelemetry.javaagent.instrumentation.undertow.UndertowExchangeGetter
• io.opentelemetry.instrumentation.spring.webflux.v5_3.WebfluxTextMapGetter

[xiepuhuan]

Would this contribution be welcome?
@trask

[trask]

hi @xiepuhuan! yes, let's start with just one (pick any), so we can work through any issues/concerns, and then you could do the rest in a single follow-up PR if you'd like to continue

[xiepuhuan]

hi @xiepuhuan! yes, let's start with just one (pick any), so we can work through any issues/concerns, and then you could do the rest in a single follow-up PR if you'd like to continue

Thank you for your reply. I will try to complete the first pull request for ExtendedTextMapGetter.