per-branch deployments

Here's a crazy idea:

1. `/routes/branch/:name`
1. `module.exports = async () => ...`
1. Clone that branch into that a `tmp` folder.
1. `return require(tmp)`

In theory, this could work!

There would need to be a ~5 minute or ~10 minute timer to kill lambdas, but that's easy.

Start by reviewing the proposed `/routes/branch/:name` entry point and the repository's existing deployment and module-loading paths. The issue suggests cloning a branch into a temporary folder, requiring it, and enforcing a five- or ten-minute lambda lifetime; done would require a decided design and an agreed way to validate per-branch deployments.

Vom Indexierungsmodell aus dem Issue-Text verfasst.