feat: app ratings endpoint

[matthew-hagemann]

New app ratings endpoint and its tests

[tim-hm]

I like this very much better than the approach I had previously!

Although interesting that you don't need a mod.rs in each sub folder?

[matthew-hagemann]

New to me, but apparently its been here for a while 😄 looks like since Rust 2018 its sufficient to just declare the sub modules in the parent directory. As you say, makes it nice to show everything we have in all the sub directories in one place! We can actually rename it from mod.rs if we want.

https://doc.rust-lang.org/edition-guide/rust-2018/path-changes.html

[tim-hm]

Looking very good! A few changes please:

• Can you run clippy locally and address the issues or disable the lint (but only when there's good reason and if we want to disable a lint then lets discuss 🙏)
• I've added some comments to address inline

Once you've made those changes send it back my way please and I'll have a more thorough tinker with the API.

[matthew-hagemann]

Looking very good! A few changes please:

* Can you run clippy locally and address the issues or disable the lint (but only when there's good reason and if we want to disable a lint then lets discuss 🙏)

* I've added some comments to address inline

Once you've made those changes send it back my way please and I'll have a more thorough tinker with the API.

Only Clippy lints left are regarding not having made use of those Config structs in our code yet, but that presumably will change in time?

Let me know if you are happy with how I did the documenting of the Wilson's score interval. Tried to keep it concise and < 80 char per line.

[tim-hm]

Excellent work.