Avoid Generator prefix

Author: yevhenii-nadtochii

java/src/main/kotlin/io/spine/validation/java/JavaValidationRenderer.kt

@@ -49,7 +49,7 @@ public class JavaValidationRenderer : JavaRenderer() {
         }
 
         val generators = listOf(
-            RequiredGenerator(querying = this, typeSystem)
+            RequiredOption(querying = this, typeSystem)
         )
 
         select(CompilationMessage::class.java).all()

java/src/main/kotlin/io/spine/validation/java/MessageValidationCode.kt

@@ -197,21 +197,23 @@ internal class MessageValidationCode(
         addLast(psiMethod)
     }
 
-    private fun validateMethodBody(rules: List<CodeBlock>, generated: List<LocalCodeBlock>): String {
+    private fun validateMethodBody(
+        rules: List<CodeBlock>,
+        generated: List<LocalCodeBlock>
+    ): String {
         if (rules.isEmpty() && generated.isEmpty()) {
             return """
                 |// This message does not have any validation constraints.
                 |return java.util.Optional.empty();
             """.trimMargin()
         }
-
         return """
             |var $violations = new java.util.ArrayList<io.spine.validate.ConstraintViolation>();
             |
             |/* Rule-based constraints. */
             |${rules.formatRules()}
             |
-            |/* Standalone constraints. */
+            |/* Standalone generated constraints. */
             |${generated.formatGenerated()}
             |
             |if (!$violations.isEmpty()) {

java/src/main/kotlin/io/spine/validation/java/RequiredOption.kt

@@ -42,7 +42,6 @@ import io.spine.protodata.java.call
 import io.spine.protodata.java.field
 import io.spine.protodata.java.mapExpression
 import io.spine.protodata.java.newBuilder
-import io.spine.protodata.java.packToAny
 import io.spine.protodata.type.TypeSystem
 import io.spine.server.query.Querying
 import io.spine.server.query.select
@@ -58,7 +57,7 @@ import io.spine.validation.java.ErrorPlaceholder.PARENT_TYPE
 import io.spine.validation.java.protodata.CodeBlock
 import io.spine.validation.protodata.toBuilder
 
-internal class RequiredGenerator(
+internal class RequiredOption(
     private val querying: Querying,
     typeSystem: TypeSystem
 ) : MessageStateValidation {