Exclude generated Sample integration tests from JaCoCo coverage

The auto-generated Sample*Test.java files are integration tests that require
real Azure credentials to run. In CI/CD pipelines without credentials, these
tests are skipped, which causes JaCoCo coverage checks to fail (0% coverage).

Solution: Exclude the Sample*Test.class files from JaCoCo coverage reporting,
since they are environment-specific integration tests and cannot be accurately
measured in all CI/CD environments. This allows the coverage checks to pass
while still maintaining proper coverage of the actual library code.

Author: Changjian Wang

sdk/contentunderstanding/azure-ai-contentunderstanding/pom.xml

@@ -47,6 +47,8 @@
     <jacoco.min.branchcoverage>0.30</jacoco.min.branchcoverage>
     <!-- Exclude generated sample files from Checkstyle validation -->
     <checkstyle.excludes>**/generated/Sample*Test.java,**/samples/Sample*.java</checkstyle.excludes>
+    <!-- Exclude generated sample test files from JaCoCo coverage (they are integration tests requiring credentials) -->
+    <jacoco.maven.plugin.excludes>**/generated/Sample*Test.class</jacoco.maven.plugin.excludes>
   </properties>
   <dependencies>
     <dependency>
@@ -72,4 +74,18 @@
       <scope>test</scope>
     </dependency>
   </dependencies>
+
+  <build>
+    <plugins>
+      <plugin>
+        <groupId>org.jacoco</groupId>
+        <artifactId>jacoco-maven-plugin</artifactId>
+        <configuration>
+          <excludes>
+            <exclude>${jacoco.maven.plugin.excludes}</exclude>
+          </excludes>
+        </configuration>
+      </plugin>
+    </plugins>
+  </build>
 </project>