@Contract(value = "_, _ -> new", pure = true)
  static @NotNull SignedMessage system(final @NotNull String message, final @Nullable ComponentLike unsignedContent) {
    return new SignedMessageImpl(message, ComponentLike.unbox(unsignedContent));
  }
Creates a system {@link SignedMessage}.

@param message the message
@param unsignedContent the optional unsigned component content
@return a new system {@link SignedMessage}
@since 4.12.0
@sinceMinecraft 1.19
api/src/main/java/net/kyori/adventure/chat/SignedMessage.java