Only first header value gets used and all other headers are thrown away on nightly Neovim

Prerequisites

[X] I am using the latest stable release of Neovim
[X] I am using the latest version of the plugin

Neovim Version

NVIM v0.11.0-dev-946+g25665b365

Operating system/version

Manjaro Linux x86_64

Actual behavior

Only the first header value is included in requests.

Expected behavior

All header values are included in the request. Expected output of :Rest curl yank:

curl -sL 'https://httpbin.org/headers' '-X' 'GET' '-H' 'Foo: foo' '-H' 'Bar: bar' '-H' 'Baz: baz' '-b' 'testcookie=foo'

Steps to reproduce

Use the following request:

GET https://httpbin.org/headers
Foo: foo
Bar: bar
Baz: baz

:Rest curl yank gives the output (notice how there's only one '-H'):

curl -sL 'https://httpbin.org/headers' '-X' 'GET' '-H' 'Foo: foo' '-b' 'testcookie=foo'

Other information

I clicked "I am using the latest stable release of Neovim" because I had to to create this issue, even though I'm on nightly. I figured this could potentially be a breaking change in Neovim that rest.nvim might have to adapt to.

Repro (`lazy.nvim`)

vim.env.LAZY_STDPATH = ".repro"
load(vim.fn.system("curl -s https://raw.githubusercontent.com/folke/lazy.nvim/main/bootstrap.lua"))()

require("lazy.minit").repro({
    spec = {
        "rest-nvim/rest.nvim",
        {
            "nvim-treesitter/nvim-treesitter",
            build = ":TSUpdate",
            main = "nvim-treesitter.configs",
            opts = {
                ensure_installed = { "http" },
                sync_install = false,
                highlight = { enable = true },
                indent = { enable = true },
            },
        },
    },
})

rest-nvim / rest.nvim