Samus let you select a file from a basic HTTP website, then launch mpv with it. It was build for personal purposes, but you're welcome!

npm i -g samus

samus <url>

You can create a .samusrc file in your $HOME directory, to specify default server / default credentials. Here is an example .samusrc:

{
  "defaultServer": {
    "url": "example.com",
    "credentials": {
      "username": "bob",
      "password": "sup3r-s3cr3t"
    }
  }
}

Now, you don't have to specify it anymore, just type:

samus