Bump openapi-generator-maven-plugin in /api-first-server (#60)

Bumps openapi-generator-maven-plugin from 6.2.1 to 6.5.0.

---
updated-dependencies:
- dependency-name: org.openapitools:openapi-generator-maven-plugin
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

api-first-server/pom.xml

@@ -71,7 +71,7 @@
             <plugin>
                 <groupId>org.openapitools</groupId>
                 <artifactId>openapi-generator-maven-plugin</artifactId>
-                <version>6.2.1</version>
+                <version>6.5.0</version>
                 <executions>
                     <execution>
                         <goals>