[issue #2221] [issue #788] Lombok now adds nullity annotations.

Which 'flavour' is defined in lombok.config; applied to toString, equals, canEqual, and plural-form of `@Singular`.

test/stubs/org/springframework/lang/Nullable.java

@@ -0,0 +1,12 @@
+package org.springframework.lang;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+@Target({ElementType.METHOD, ElementType.PARAMETER, ElementType.FIELD})
+@Retention(RetentionPolicy.RUNTIME)
+@Documented
+public @interface Nullable {}