added octoprint documentation

doc/OCTOPRINT.md

@@ -0,0 +1,51 @@
+# README
+
+This document describes how to use the Signal Messenger REST API together with Octoprint. 
+
+prerequisites:
+* docker + docker-compose
+* a phone number to send signal notifications
+
+## Set up the docker container
+
+* Create a `docker-compose.yml` file with the following contents: 
+
+```
+version: "3"
+services:
+  signal-cli-rest-api:
+    image: bbernhard/signal-cli-rest-api:latest
+    ports:
+      - "8080:8080" # map docker port 8080 to host port 8080.
+    network_mode: "host"
+    volumes:
+      - "./signal-cli-config:/home/.local/share/signal-cli" # map "signal-cli-config" folder on host system into docker container. the folder contains the password and cryptographic keys when a new number is registered
+```
+
+* start the docker container with `docker-compose up`
+
+
+## Register phone number
+
+In order to send signal messages to other users, you first need to register your phone number. This can be done via REST requests with: 
+
+
+```curl -X POST -H "Content-Type: application/json" 'http://<ip>:<port>/v1/register/<number>'```
+
+e.g: 
+
+This registers the number `+431212131491291` to the Signal network.
+
+```curl -X POST -H "Content-Type: application/json" 'http://127.0.0.1:8080/v1/register/+431212131491291'```
+
+After you've sent the registration request, you will receive a token via SMS for verfication. In order to complete the registration process you need to send the verification token back via the following REST request: 
+
+```curl -X POST -H "Content-Type: application/json" 'http://<ip>:<port>/v1/register/<number>/verify/<verification code>'```
+
+e.g:
+
+```curl -X POST -H "Content-Type: application/json" 'http://127.0.0.1:8080/v1/register/+431212131491291/verify/123-456'```
+
+
+# Troubleshooting
+In case you've problems with the `signal-cli-rest-api` container, have a look [here](TROUBLESHOOTING.md)