Fix GHSA-45q3-82m4-75jr: force netty-handler-proxy to 4.2.13.Final

Added resolutionStrategy.eachDependency override in build.gradle to
upgrade io.netty:netty-handler-proxy from 4.2.12.Final to 4.2.13.Final.

netty-handler-proxy is a transitive dependency via
io.projectreactor.netty:reactor-netty-core. The fix follows the existing
pattern for security overrides already present in build.gradle.

Fixes: GHSA-45q3-82m4-75jr (HTTP Header Injection in HttpProxyHandler)

Agent-Logs-Url: https://github.com/getyourguide/openapi-validation-java/sessions/31fddbbb-e4eb-48ae-b567-a7a5663459e3

Co-authored-by: gygrobot <19344429+gygrobot@users.noreply.github.com>

Author: Copilot

build.gradle

@@ -35,6 +35,11 @@ subprojects {
                 useVersion('11.0.21')
                 because('GHSA-rv64-5gf8-9qq8 / GHSA-x4m4-345f-5h5g / GHSA-24j9-x2wg-9qv6: Apache Tomcat < 11.0.21 vulnerabilities')
             }
+            if (requested.group == 'io.netty' && requested.name == 'netty-handler-proxy'
+                    && requested.version != null && requested.version < '4.2.13.Final') {
+                useVersion('4.2.13.Final')
+                because('GHSA-45q3-82m4-75jr: HTTP Header Injection vulnerability in netty-handler-proxy < 4.2.13.Final')
+            }
         }
     }