TYPO3 Core

After PageRouter->generateUri() has created a link to a page, an event should be dispatched that allows extensions to react to the created URI or modify it.

Whenever an extension author modifies a generated URL they would need to take care that the URL can be resolved again in the end.

Use Case 1 (URL modification):
Via event the generated page URI is modified in a way that url path slugs are rearranged. Once this modified URI is called, a middleware recognizes it and modifies it back, so TYPO3 can resolve it again.

Use Case 2 (URL Logging):
Sometimes you have errors reported or in your logs, where you ask yourself: How did anyone end up on that URL? Where and why was it generated? So it could be useful to maintain a log with debugging information whenever a new URI is generated.