Currently, flatc allows using --rust-module-root-file and --gen-all to generate multiple schemas into a single crate with a top-level mod.rs. This is good but makes it really hard to use in many contexts since the best (only?) option to have inter-dependent schemas is to generate everything together into a single crate.

Ideally, we can generate each schema independently of the includes (as each include will be its own generated crate), and link them all at build time.