docs: private void validateField(VariableElement injectedField) {
      if (injectedField.getModifiers().contains(Modifier.PRIVATE)) {
        messager.printMessage(Kind.ERROR,
            "Property "
                + injectedField.getSimpleName()
                + " in "
                + injectedField
                .getEnclosingElement()
                .getSimpleName()
                + " cannot be injected and private. Please make it at least package protected.");
      }
      if (injectedField.getModifiers().contains(Modifier.FINAL)) {
        messager.printMessage(Kind.ERROR,
            "Property " + injectedField.getSimpleName() + " in " + injectedField
                .getEnclosingElement()
                .getSimpleName() + " cannot be injected and final.");
      }
    }