Add URI template support to ProxyExchange for observability

[fru1tworld]

ProxyExchange.exchange() used rest.exchange(RequestEntity, ...) which loses
the URI template pattern, causing Micrometer http.client.requests uri tag
to always be "none".

Add uri(String, Map) overload that preserves the template so RestTemplate
can pass it to Micrometer.

Fixes #3458

[Copilot]

Pull request overview

This PR fixes missing URI template observability for MVC ProxyExchange backend calls by preserving the URI template pattern through to RestTemplate, enabling Micrometer’s http.client.requests uri tag to be populated (instead of "none").

Changes:

• Add a ProxyExchange.uri(String uriTemplate, Map<String, ?> uriVariables) overload that stores the template + variables and expands to a concrete URI.
• Update ProxyExchange.exchange(...) to call RestTemplate.exchange(String, ...) when a template is available, preserving the URI template for observability.
• Add an integration test asserting that the http.client.requests metric contains uri="/foos/{id}" when using the new overload.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
spring-cloud-gateway-proxyexchange-webmvc/src/main/java/org/springframework/cloud/gateway/mvc/ProxyExchange.java	Introduces URI-template-aware uri(...) overload and routes exchanges through RestTemplate.exchange(String, ...) to preserve template metadata for Micrometer.
spring-cloud-gateway-proxyexchange-webmvc/src/test/java/org/springframework/cloud/gateway/mvc/ProductionConfigurationTests.java	Adds coverage validating that URI template usage results in a templated uri tag in http.client.requests.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[ryanjbaxter]

Please sign your commit and also submit this against the 4.3.x branch

[fru1tworld]

Rebased onto 4.3.x and signed the commit. Thanks for the feedback!