Middleware proposal for `foundry-fork-db`

[Karrq]

We recently had to fork foundry-fork-db as the functionality in shared backend was moved there. This must somehow be proposed back to upstream to, for example, seamlessly allow adding additional middlewares so we can encode our functionality as an “extension” instead of necessitating a fork

[dutterbutter]

Some work has begun here: foundry-rs/foundry-fork-db@main...dutterbutter:foundry-fork-db:db/add-custom-req

[dutterbutter]

Closed in #792