proxy: add JWT request signing support (#19)

- Refactored middleware and request hander logging.
- Request refactored to use context.Context.
- Add helper (based on Alice) to allow middleware chaining.
- Add helper scripts to generate elliptic curve self-signed certificate that can be used to sign JWT.
- Changed LetsEncrypt scripts to use acme instead of certbot.
- Add script to have LetsEncrypt sign an RSA based certificate.
- Add documentation to explain how to verify headers.
- Refactored internal/cryptutil signer's code to expect a valid EC priv key.
- Changed JWT expiries to use default leeway period.
- Update docs and add screenshots.
- Replaced logging handler logic to use context.Context.
- Removed specific XML error handling.
- Refactored handler function signatures to prefer standard go idioms.

internal/https/https.go

@@ -130,6 +130,8 @@ func readCertificateFile(certFile, certKeyFile string) (*tls.Certificate, error)
 }
 
 // newDefaultTLSConfig creates a new TLS config based on the certificate files given.
+// see also:
+// https://wiki.mozilla.org/Security/Server_Side_TLS#Recommended_configurations
 func newDefaultTLSConfig(cert *tls.Certificate) (*tls.Config, error) {
 	tlsConfig := &tls.Config{
 		CipherSuites: []uint16{