Update docs to Expression addons

Author: yevhenii-nadtochii

java/src/main/kotlin/io/spine/validation/java/protodata/CodeBlock.kt

@@ -31,7 +31,7 @@ import io.spine.protodata.java.Statement
 import io.spine.string.joinByLines
 
 /**
- * A list of Java statements.
+ * Represents one or more Java statements.
  *
  * An example of creating a code block:
  *
@@ -43,6 +43,7 @@ import io.spine.string.joinByLines
  *         var violation = createViolation(fieldPath);
  *         violations.add(violation);
  *     }
+ *     return violations;
  *     """.trimIndent()
  * )
  * ```

java/src/main/kotlin/io/spine/validation/java/protodata/MemberDeclaration.kt

@@ -30,10 +30,7 @@ import io.spine.protodata.java.AnElement
 
 /**
  * Represents class level member declaration.
+ *
+ * A class body may contain declarations of fields, methods, classes, and interfaces.
  */
-// TODO:2025-01-31:yevhenii.nadtochii: Add `MethodDeclaration`. Also, `FieldDeclaration` is not
-//  a statement, it should become a declaration too.
-// TODO:2025-01-31:yevhenii.nadtochii: Consider adding `Context<T>`. So, that instead of
-//  `Expression<Message>.call("getField")` we could use `Context<Message>.call("getField").
-//  We don't really an explicit `this` in the class context. It harms readability a bit.
 public open class MemberDeclaration(code: String) : AnElement(code)