Performance issues introduced by nested exposures

[jure]

So for some reason, grape-entity has become really slow for me recently. I played a bit with the nested exposures code and if I disable them (my entities don't have them), performance increases dramatically, we're talking API response goes from 900ms to 50ms for 25 records.

Here's the stuff I disabled: https://github.com/jure/grape-entity/commit/a46c7d5019cfbc856eb5b51ea730a9e17272108a

I would love to explore these issues more thoroughly, perhaps someone can guide me in the right direction.

[dblock]

This clearly has to do with nested exposures. We need a different way to find nested exposures than the current regex mechanism. They need to be flagged with a boolean and not retrieved time-and-again. Please feel free to contribute, I also will take a look.

There's a related discussion in #58.

[jure]

With #60 and #61, performance has increased dramatically, so I'm closing this. Thanks @AlexYankee!