get route info in spring-cloud-gateway with opentelemetry-spring-boot-starter

Describe the bug

Metrics for dynamic routes exposed by Spring Cloud Gateway do not include the http.route attribute. The same issue was previously found in the Java agent and addressed here: https://github.com/open-telemetry/opentelemetry-java-instrumentation/pull/9597

Steps to reproduce

Create a spring cloud gateway application with 'io.opentelemetry.instrumentation:opentelemetry-spring-boot-starter'

Expected behavior

http.route attribute filled with the correct information

Actual behavior

While using spring-cloud-gateway, we always get null http.route because spring-cloud-gateway does not put the HandlerMapping.BEST_MATCHING_PATTERN_ATTRIBUTE in exchange object,

Javaagent or library instrumentation version

opentelemetry-spring-boot-starter 2.18.1

Environment

JDK: 21
OS: macOs 15:4
Spring Cloud Gateway: 2023.0.0
opentelemetry-spring-boot-starter: 2.18.1

Additional context

No response

Tip

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Start by reproducing the issue with Spring Cloud Gateway and opentelemetry-spring-boot-starter, then read the referenced Java agent pull request for its handling of dynamic routes. The work is complete when dynamic gateway routes report the correct http.route attribute instead of null.