Set $VERSION statically in curl installer

[EverlastingBugstopper]

right now it's required to have a $VERSION variable set before the curl installer works. this should be set automatically either in our release process by parsing from Cargo.toml, or by the installer itself checking for $VERSION and then making a separate HTTP request to figure out the latest version released on github. i'm not sure which one i like better, the first one is more performant (eliminates one round trip to github), whereas the second one might be a bit easier.

[EverlastingBugstopper]

@jbaxleyiii had this idea which would work just fine

[jbaxleyiii]

This should mostly be supported already via spaceport.

1. We need to adjust the url to the rover repo here https://github.com/apollographql/spaceport/blob/main/src/routes/cli.ts#L6
2. Ensure that the binary matches the naming here (or actually change it (for instance ap needs to be rover) https://github.com/apollographql/spaceport/blob/main/src/routes/cli.ts#L35) and send the correct platform as part of the request https://github.com/apollographql/spaceport/blob/main/src/routes/cli.ts#L9
3. As a backup, it would be great to upload the binaries straight to cloudflare storage so that our cache is already warm https://github.com/apollographql/spaceport/blob/main/src/routes/cli.ts#L36

The benefit here is we have edge caching and usage analtyics already built in https://github.com/apollographql/spaceport/blob/main/src/routes/cli.ts#L40-L51 and the CLI / shell scripts can be much simpler.

[JakeDawkins]

After looking at this, it feels weird to me that an install script (which itself is versioned and released with versioned tags) would be responsible for downloading/installing any version of Rover. I think it makes more sense to have the script be static, and use another source, like spaceport, to point at the right script.

So curl -sSL https://raw.githubusercontent.com/apollographql/rover/v0.0.2/installers/binstall/scripts/nix/install.sh | sh would always download and install v0.0.2 of Rover.