tracker: wasm support in fastn.app readiness

[amitu]

Status:

• mounting wasm files from app
• ftd.app-path(path="/asd/") (@siddhantk232 is working on this at ftd.app-path function #2057)
• wasm accessing system config and other wasm apis #2054

Future

• honouring wasm+proxy from app
• auto mounting wasm files in current package
  • dont auto mount wasm files in /downloads/ folder (explicitly mount allowed)
• ftd files to have higher priority than wasm
• ft_sdk::mount_relative("/asd/")

---

Currently we have to add an entry in dynamic-urls to mount a wasm file, eg:

-- fastn.url-mappings:

/ft-wasm/* -> wasm+proxy://sample.wasm/*

We can auto mount any URL, so if a file sample.wasm is present in a fastn package, we will implicitly assume

-- fastn.url-mappings:

/sample/* -> wasm+proxy://sample.wasm/*

Is added.

We will still allow wasm+proxy to take care of scenario that you want to mount a wasm on a path that is not derived from its file name.

Priority to ftd files

If we have a file api.wasm, and a file api/foo.ftd, any request to /api/foo/ will be handled by api/foo.ftd, and any other /api/* will go to wasm.

No wasm execution in downloads folder

If any wasm file is in /downloads/ folder tree, it will not be executed. Explicit wasm+proxy: binding will be required for them if that is needed.

ftd.mount-relative(url="/asd/") & ft_sdk::mount_relative("/asd/")

We will create a ftd built in function and a ft_sdk function to convert a relative url to full url, eg if app is mounted on /app/ the above will return /app/asd/.