Using last modified for static resources in reproducible archives and images causes unwanted browser caching

[bclozel]

In spring-projects/spring-framework#25845, Spring Framework introduced a new option for serving static resources that enables/disables usage of the last modified file metadata when serving static resources.

As described in the Framework issue, this can lead to problems when applications are packaged as container images and files metadata are changed for caching or reproducibility. Since Spring Boot now builds application as container images using Cloud Native Buildpacks, we should consider this as a bug since Spring Boot users have no way to change that without writing a fair amount of code.

Adding this option will enable developers to switch it on in environments where file metadata is overwritten.