Optimisation for backend by caching requests for users.

[bobdenotter]

As pointed out by @rossriley: No need to fetch users every single time. This PR fetches them once, and returns from memory if possible. This yields a significant improvement in queries / time taken.

Before:

After:

[bobdenotter]

Would you look at that!

[rossriley]

Can we have 2.2 version too... this is awesome.

[bobdenotter]

@rossriley Surely. I'll backport this to 2.2.x after it has landed.

[GwendolenLynch]

Just a few issues I am looking at 😁

[GwendolenLynch]

@bobdenotter acceptance tests were broken due to the permissions changes. I have modified the flow a bit and it passes locally… So back over to you for approval I guess.

Note: With your original changes, we already know if we have a \Bolt\Content object and isAllowedSingle() only cares about the owner ID at that point anyway, which we will have if either an object of array has been passed into isAllowed() in the first place… so we're not needed to re-request the object at that stage… Query count unchanged.

[bobdenotter]

Hooray for teamwork! 🎉

[bobdenotter]

Booom!