Add caching of CSS

Problem/Motivation

Follow-on issue from 📌 Drupal 10.1.0 new aggregation breaks InlineCssEmailAdjuster Needs review . The new Drupal 10.1 aggregation mechanism actually has the opposite performance effect for this module - we lose caching that was previously available. Therefore we need to create our own caching mechanism if performance is a concern.

See 📌 Add an API method to get the contents of a CSS or JavaScript aggregate from a URL Closed: works as designed . The response from the Core maintainers is that it should be possible to add back caching in about 15 lines of code using supported Core API functions. If anyone would like to try that please create patches on this issue. If we believe this isn't possible, then we can go back and ask for a new API.

Patches won't be accepted if they use unofficial Core functions, depend on implementation details of Core, or are much more than 15 lines of code.

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes