Obtain the referrer URL or referrer query via a token

I just came across the same requirement and implemented that in the MR above. Please review.

This would need to consider cacheability metadata for http headers, which I'm not sure is reliably possible as page cache for example won't rely on that.

Ajax should maybe have its own handling, similar to what views already does in its ajax controller.

However, I have found that almost all ajax modules do not support tokens, such as block_ajax → , ajax_big_pipe → , io → , quicktabs → . When I enable them, if a token is used in them, it will be invalidated, it blocks the retrieval of data from the current page. However, if I close ajax, everything becomes normal again, I haven't seen any Ajax modules using caching to solve this problem.