Mark final fields as such (#159)

This also makes some LOGGER declarations static.

Author: findepi

polaris-service/src/test/java/io/polaris/service/PolarisApplicationIntegrationTest.java

@@ -91,7 +91,7 @@ public class PolarisApplicationIntegrationTest {
       LoggerFactory.getLogger(PolarisApplicationIntegrationTest.class);
 
   public static final String PRINCIPAL_ROLE_NAME = "admin";
-  private static DropwizardAppExtension<PolarisApplicationConfig> EXT =
+  private static final DropwizardAppExtension<PolarisApplicationConfig> EXT =
       new DropwizardAppExtension<>(
           PolarisApplication.class,
           ResourceHelpers.resourceFilePath("polaris-server-integrationtest.yml"),

polaris-service/src/test/java/io/polaris/service/catalog/PolarisRestCatalogIntegrationTest.java

@@ -106,7 +106,7 @@ public class PolarisRestCatalogIntegrationTest extends CatalogTests<RESTCatalog>
   private static final String S3_BUCKET_BASE =
       Optional.ofNullable(System.getenv("INTEGRATION_TEST_S3_PATH"))
           .orElse("file:///tmp/buckets/my-bucket");
-  private static DropwizardAppExtension<PolarisApplicationConfig> EXT =
+  private static final DropwizardAppExtension<PolarisApplicationConfig> EXT =
       new DropwizardAppExtension<>(
           PolarisApplication.class,
           ResourceHelpers.resourceFilePath("polaris-server-integrationtest.yml"),

polaris-service/src/test/java/io/polaris/service/catalog/PolarisRestCatalogViewIntegrationTest.java

@@ -76,7 +76,7 @@ public class PolarisRestCatalogViewIntegrationTest extends ViewCatalogTests<REST
   public static final String S3_BUCKET_BASE =
       Optional.ofNullable(System.getenv("INTEGRATION_TEST_S3_PATH"))
           .orElse("file:///tmp/buckets/my-bucket");
-  private static DropwizardAppExtension<PolarisApplicationConfig> EXT =
+  private static final DropwizardAppExtension<PolarisApplicationConfig> EXT =
       new DropwizardAppExtension<>(
           PolarisApplication.class,
           ResourceHelpers.resourceFilePath("polaris-server-integrationtest.yml"),

polaris-service/src/test/java/io/polaris/service/catalog/PolarisSparkIntegrationTest.java

@@ -69,7 +69,7 @@ public class PolarisSparkIntegrationTest {
 
   public static final String CATALOG_NAME = "mycatalog";
   public static final String EXTERNAL_CATALOG_NAME = "external_catalog";
-  private static S3MockContainer s3Container =
+  private static final S3MockContainer s3Container =
       new S3MockContainer("3.9.1").withInitialBuckets("my-bucket,my-old-bucket");
   private static PolarisConnectionExtension.PolarisToken polarisToken;
   private static SparkSession spark;

polaris-service/src/test/java/io/polaris/service/task/TestSnapshot.java

@@ -31,11 +31,11 @@
 import org.apache.iceberg.io.FileIO;
 
 final class TestSnapshot implements Snapshot {
-  private long sequenceNumber;
-  private long snapshotId;
-  private long parentSnapshot;
-  private long timestampMillis;
-  private String manifestListLocation;
+  private final long sequenceNumber;
+  private final long snapshotId;
+  private final long parentSnapshot;
+  private final long timestampMillis;
+  private final String manifestListLocation;
 
   public TestSnapshot(
       long sequenceNumber,