Add middleware cache for Content Search API parsed IIIF Manifest.

[DiegoPino]

What?

All cool/nice/smooth when searching across 200 pages. Super slow on 767+ pages *also... that is a large manifest people. Why?

Solution is:

• Reuse the Metadata Exposed API caching mechanism, but instead of caching the actual IIIF Manifest (which will still require parsing via JMESPATH a 2.9 Mbytes (*for the 767 pages manifest expressed in this message) for every query YET again, we cache the already cleaned/processed JMESPATH results.

Caches will clear, of course as always, if the NODE or the Exposed endpoint or the IIIF Manifest itself changes.

@alliomeria, life is hard...

This connects with #456 of course.

I almost feel tempted to allow people for these beast of ADOs to donwload the Manifest, upload back as file. Serve statically until the end of days (which is a manual version of #456 )