Added documentation for ZeroSSL.

docs/zerossl.md

@@ -0,0 +1,70 @@
+# ZeroSSL
+
+EasyHAProxy can issue a ZeroSSL certificate. Follow the steps below:
+
+## Getting the Keys from ZeroSSL
+
+- Login to [ZeroSSL](https://zerossl.com?fpr=byjg)
+- If you don't have an account you can use our referral link: [https://zerossl.com?fpr=byjg](https://zerossl.com?fpr=byjg)
+- If you created recently and would like to support us open an issue, and I'll try to add you as our referred.
+- In the ZeroSSL dashboard click in 'Developer' and the Generate EAB Keys
+
+![zerossl_1.png](zerossl_1.png)
+
+- Once you generate the keys, please **take note**. We will need this later, and it isn't saved anywhere.
+
+![zerossl_2.png](zerossl_2.png)
+
+```text
+Important: if you to this process again the old values will be lost and you need to setup EasyHAProxy again.
+```
+
+## Setting up EasyHAProxy
+
+Run the EasyHAProxy container with the following parameters:
+
+```bash
+docker run \
+    ... \
+    -e EASYHAPROXY_CERTBOT_EMAIL="your zerossl email" \
+    -e EASYHAPROXY_CERTBOT_EAB_KID="the eab_kid from the previous step" \
+    -e EASYHAPROXY_CERTBOT_EAB_HMAC_KEY="the eab_hmac_key from the previous step" \
+    -e EASYHAPROXY_CERTBOT_SERVER="https://acme.zerossl.com/v2/DV90" \
+    -p 80:80 \
+    -p 443:443 \
+    -v /path/to/guest/certbot/certs:/certs/certbot \
+    ... \
+    byjg/easy-haproxy
+```
+
+Notes:
+
+- If you don't setup all `EASYHAPROXY_CERTBOT_*` environment variables with the proper values, EasyHAProxy will fail silently and **will not request** a certificate.
+- The ports 80 and 443 needs to accessible through the internet as [Let's Encrypt requirement](https://letsencrypt.org/docs/allow-port-80/)
+
+**It is required you to persist the container folder `/certs/certbot` outside the container.**
+
+You cannot delete or change it contents. 
+If you do not persist, or change/delete the contents, Let's encrypt will not work properly. 
+
+
+## Setting up your container to use ZeroSSL
+
+```bash
+docker run \
+    ... \
+    --label easyhaproxy.express.port=80 \
+    --label easyhaproxy.express.localport=3000 \
+    --label easyhaproxy.express.host=example.org \
+    --label easyhaproxy.express.certbot=true \
+    ... \
+    some/myimage
+```
+
+Requirements:
+
+- Your container **must** listen to port 80. Letsencrypt will not issue the certificate if `easyhaproxy.<definition>.port` is in another port, and EasyHAProxy will fail silently.
+- You cannot set port 443 for the container with the Letsencrypt because EasyHAProxy will create this port automatically once the certificate is issued.
+
+----
+[Open source ByJG](http://opensource.byjg.com)