"Accessory checkout" version of checkout accessories to locations

[uberbrady]

For being able to 'checkout to ___location' as well as 'checkout to user' for Accessories, a lot of the fundamentals of how those relationships work needs to change. This is one attempt at getting those relationships to sort-of work right.

At this point, I can go into Tinker and, from an Accessory, look at AccessoryCheckouts which can point to users or locations. As well as going the other directions.

The extra level of indirection is a little awkward when running through the relationships, which is why I figured MorphedByMany approach might be better - but, in fact, it's so much worse :(

This is by no means complete, but at least the basic relationships seem to work at the model level.

[what-the-diff]

PR Summary

• Comment Addition in Accessory.php
  Added explanatory comments to enhance code readability and clarify functionality.

• Comment Correction in AccessoryCheckout.php
  Revised a previously incorrect comment to ensure accurate reflection of the function’s purpose.

• New Method in Location.php
  Added a new method assignedAccessories(). This function expands our program's capabilities by helping track accessories assigned to various locations.

• Comment Addition in User.php
  Added another comment to clarify the purpose of a block of code, thus boosting overall code maintenance and readability.