Rack middleware for Omeka 2.3.1: are there any examples?

[Douglas Duhaime]

I'm sorry to post so many queries in a row, but this third seems sufficiently different from the former two that I thought it should have a unique thread as well.

Are there any examples of rack middleware within the Omeka 2.3.x stack? I'm starting to think this will be the best way to perform some application logic before servicing requested routes, but I'm not sure where to look for examples or guidance.

If I wanted to dip into the Zend framework to introduce some custom middleware within an Omeka 2.3.1 application, does anyone have any tips on how to proceed? Here is evidently a deck on rack middleware for Zend 3: http://www.zimuel.it/slides/phpday2016/#/9 If this kind of approach is a viable option, which Zend build should one plan to target within Omeka 2.3.1? I would be very grateful for any documentation or advice others can offer on this thread!