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.

scripts/generate_wildcard_cert.sh

@@ -1,11 +1,16 @@
 #!/bin/bash
 
-# requires certbot
-certbot certonly --manual \
-	--agree-tos \
-	-d *.corp.example.com \
-	--preferred-challenges dns-01 \
-	--server https://acme-v02.api.letsencrypt.org/directory \
-	--config-dir le/config \
-	--logs-dir le/work \
-	--work-dir le/work
+# requires acme.sh
+# see : https://github.com/Neilpang/acme.sh
+# uncomment below to install
+# curl https://get.acme.sh | sh
+
+# assumes cloudflare, but many DNS providers are supported
+
+export CF_Key="x"
+export CF_Email="x@x.com"
+
+$HOME/.acme.sh/acme.sh \
+	--issue \
+	-d '*.corp.beyondperimeter.com' \
+	--dns dns_cf