Explain mandatory TLS, describe solution

We've gotten frequent requests to offer a method of disabling TLS. We're
not comfortable doing this because it could easily result in
less-technical users shooting themselves in the foot.

The new documentation points more technical users at a solution.

Author: Seth Terashima

README.md

@@ -236,6 +236,14 @@ openssl req -x509 -nodes -newkey ec \
 
 This command creates an unencrypted private key, `config/tls-key.pem`.
 
+The proxy server requires TLS. We do not offer an option to disable TLS because
+this greatly increases the risk of non-experts creating insecure deployments.
+Expert users who need a non-TLS version can create one without forking the
+repository by using
+[pkg/proxy](https://pkg.go.dev/github.com/teslamotors/vehicle-command/pkg/proxy);
+the [proxy source code](cmd/tesla-http-proxy/main.go) may be a helpful starting
+point.
+
 ### Running the proxy server
 
 The proxy server can be run using the following command:

cmd/tesla-http-proxy/main.go

@@ -69,6 +69,18 @@ func Usage() {
 }
 
 func main() {
+	// ******************************************************************************************
+	// WHY IS THERE NO OPTION FOR DISABLING TLS?
+	// ******************************************************************************************
+	// In the past, we have had problems with third-party applications that made it easy for DIY
+	// enthusiasts to inadvertently expose their vehicles to the public Internet. In order to
+	// protect users who do not understand the risks of disabling TLS, we decided to omit an
+	// --insecure flag or similar.
+	//
+	// Expert users who need to disable TLS can do so without forking this repository by using the
+	// pkg/proxy package, which is agnostic to TLS. This application is a very thin wrapper around
+	// that package.
+
 	config, err := cli.NewConfig(cli.FlagPrivateKey)
 
 	if err != nil {