Create schema for the API (#28)

* feat(schema): add basic structs for schema

* feat(schema): implement base62 id parsing

* docs(schema): add documentation for schema structs
fix(schema): prevent integer overflow in base62 decoding

* refactor(schema): move ids into submodules, reexport from ids mod

* feat(schema): add random generation of base62 ids
style: run rustfmt

src/models/error.rs

@@ -1,4 +1,6 @@
 use serde::{Deserialize, Serialize};
+
+/// An error returned by the API
 #[derive(Serialize, Deserialize)]
 pub struct ApiError<'a> {
     pub error: &'a str,