Provide an AbstractApiProvider to clean up paths

[JasonTheAdams]

There are many places where a provider/model sets the various API endpoint paths. Each places concatenates the path and uses things like ltrim(). It's redundant and opens up for simple mistakes. It would be great to have an AbstractApiProvider class (and likely a corresponding provider interface) that is aware of a base URL and has an AbstractApiProvider::url($path) counterpart, which cleans this up.

[felixarntz]

@JasonTheAdams Let's implement this this week, ideally to release in 0.2.0. I'd love to do a fast follow with some crucial enhancements and fixes, maybe we can already release end of this week or beginning of next week.

[felixarntz]

@JasonTheAdams That last comment didn't age well 😆

Do you think you have bandwidth for this this week? Otherwise I think we can also punt this to 0.3.0, it's not urgent to have in this release, since it's mostly an internal DX improvement that will only affect extenders.

[JasonTheAdams]

@felixarntz Looking at the code, I'm trying to think of the best place to introduce something like this. I'm thinking one of two paths:

1. Create a WithApiRequestTrait that just adds the property and method, so its composable
2. Create an AbstractApiProvider, like described, and have AbstractApiBasedModelMetadataDirectory extend it, which the current API providers implement

I just noticed there's a lot of inheritance currently happening with those Providers, and if this fits in that stack neatly. As the person who made them, I'd love your input as to which you like best.

[felixarntz]

@JasonTheAdams I think AbstractApiProvider is most intuitive for now. If we find composability with a trait useful at some point, we can still pull that out then and keep using it in the abstract class, so it seems most straightforward to avoid the trait for now.

[JasonTheAdams]

Ignore what I was saying in point 2 above. I wasn't paying attention to the fact that AbstractApiBasedModelMetadataDirectory isn't the provider, it just uses the provider to construct the URL.