Implement a caching strategy on KIE Sandbox container image

[thiagoelg]

When updating KIE Sandbox versions users might still see the old version cached by their browsers.

In this task, we should study possible methods to avoid these situations on both the live version (sandbox.kie-org) and the containerized version (via kie-sandbox-image), and implement the best one.

It's important to note that cached files shouldn't be invalidated if there are no changes.

Good reference materials:

• https://httpd.apache.org/docs/2.4/caching.html
• https://webpack.js.org/guides/caching/
• https://developer.mozilla.org/en-US/docs/Web/HTTP/Caching
• https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/ETag

[porcelli]

maybe ETag helps here