enable NullAway option RequireExplicitNullMarking to detect classes that are not annotated with JSpecify annotations

Author: ThoSap

build.gradle.kts

@@ -83,6 +83,7 @@ subprojects {
 
         options.errorprone {
             check("NullAway", CheckSeverity.ERROR)
+            check("RequireExplicitNullMarking", CheckSeverity.ERROR)
             option("NullAway:AnnotatedPackages", "it.aboutbits.postgresql")
             option("NullAway:JSpecifyMode", "true")
         }

operator/src/test/java/it/aboutbits/postgresql/_support/valuesource/BlankSource.java

@@ -1,5 +1,6 @@
 package it.aboutbits.postgresql._support.valuesource;
 
+import org.jspecify.annotations.NullMarked;
 import org.junit.jupiter.params.provider.ValueSource;
 
 import java.lang.annotation.Documented;
@@ -12,5 +13,6 @@
 @Retention(RetentionPolicy.RUNTIME)
 @Documented
 @ValueSource(strings = {"", " ", "         ", "\t", "\r", "\n", "\r\n", "\f", "\u000B"})
+@NullMarked
 public @interface BlankSource {
 }