[fix] force Vite dev mode to use HTTP/1 for TLS

[Conduitry]

This fixes #3479 by adding a no-op server.proxy config to Vite in dev mode to force it to downgrade to TLS-only when HTTPS in enabled, rather than using HTTP/2. node-fetch's Request implementation did not like the HTTP/2 headers it was getting.

Arguably, we could only apply this server.proxy config when --https is enabled. I'd be up for making that change if someone else thinks it worthwhile.

I'm not entirely thrilled with this solution, but it seemed the best one at the moment. We may need to revisit how node-fetch deals with HTTP/2 headers at some point in the future.

I'm not sure how to test this nicely, so there isn't one, and I would appreciate someone else taking this for a spin.

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[benmccann]

Looks like there's an open issue in the node-fetch repo for HTTP/2 support: node-fetch/node-fetch#342

[Conduitry]

It sounds like we shouldn't be holding our breath for that. I'm not sure to what extent we actually need HTTP/2 support and to what extent we just need it to not complain about HTTP/2-style headers when instantiating Request instances. I'd rather not fork node-fetch at this point, although there eventually may be enough compelling reasons to do so.

In any case, I think the workaround in this PR is a reasonable solution for now. My main fear is that Vite will eventually change its behavior around server.proxy and HTTP/2, or that it will become smarter, and realize that server.proxy = {} doesn't really necessitate any changes. If that happens, I hope we have some other way of controlling HTTP/1 vs HTTP/2, because - besides the node-fetch thing - I'm thinking HTTP/2 will be introducing other unnecessary complexities into local development.

[Conduitry]

I've gone ahead and made the change I mentioned in the OP - I'm now only setting server.proxy to {} when server.https is present and server.proxy is absent.

[nstuyvesant]

From my perspective, this is a good short-term fix.