Add nullability annotations to tests in module/spring-boot-data-r2dbc-test

See gh-47263

module/spring-boot-data-r2dbc-test/build.gradle

@@ -37,3 +37,7 @@ dependencies {
 
 	testRuntimeOnly("ch.qos.logback:logback-classic")
 }
+
+tasks.named("compileTestJava") {
+	options.nullability.checking = "tests"
+}

module/spring-boot-data-r2dbc-test/src/test/java/org/springframework/boot/data/r2dbc/test/autoconfigure/Example.java

@@ -16,6 +16,8 @@
 
 package org.springframework.boot.data.r2dbc.test.autoconfigure;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.data.annotation.Id;
 import org.springframework.data.relational.core.mapping.Table;
 
@@ -28,6 +30,6 @@ import org.springframework.data.relational.core.mapping.Table;
 public class Example {
 
 	@Id
-	String id;
+	@Nullable String id;
 
 }