feat: initial README, fixes #5

Signed-off-by: Chris Gianelloni <[email protected]>

Author: wolf31o2

README.md

@@ -1 +1,56 @@
-# go-cardano-submit-api
+# go-cardano-submit-api
+Cardano Transaction Submission API
+
+A simple HTTP API which accepts a CBOR encoded Cardano transaction as a
+payload body and submits it to a Cardano full node using the Ouroboros
+LocalTxSubmission Node-to-Client (NtC) protocol.
+
+## Usage
+The recommended method of using this application is via the published
+container images.
+
+```
+docker run -p 8090 ghcr.io/cloudstruct/cardano-submit-api:0.4.0
+```
+
+### Configuration
+Configuration can be done using either a `config.yaml` file or setting
+environment variables. Our recommendation is environment variables.
+
+#### Environment variables
+Configuration via environment variables can be broken into two sets of
+variables. The first set controls the behavior of the application, while the
+second set controls the connection to the Cardano node instance.
+
+Application configuration:
+`API_LISTEN_ADDRESS` - Address to bind for API calls, all addresses if empty (default: empty)
+`API_LISTEN_PORT` - Port to bind for API calls (default: 8090)
+`DEBUG_ADDRESS` - Address to bind for pprof debugging (default: localhost)
+`DEBUG_PORT` - Port to bind for pprof debugging, disabled if 0 (default: 0)
+`LOGGING_LEVEL` - Logging level for log output (default: info)
+`METRICS_LISTEN_ADDRESS` - Address to bind for Prometheus format metrics, all
+    addresses if empty (default: empty)
+`METRICS_LISTEN_PORT` - Port to bind for metrics (default: 8081)
+
+Connection to the Cardano node can be performed using specific named network
+shortcuts for known network magic configurations. Supported named networks are:
+
+- mainnet
+- preprod
+- preview
+- testnet
+
+You can set the network to an empty value and provide your own network magic to
+connect to unlisted networks.
+
+TCP connection to a Cardano node without using an intermediary like SOCAT is
+possible using the node address and port. It is up to you to expose the node's
+NtC communication socket over TCP. TCP connections are preferred over socket
+within the application.
+
+Cardano node configuration:
+`CARDANO_NETWORK` - Use a named Cardano network (default: mainnet)
+`CARDANO_NODE_ADDRESS` - Address to Cardano node NtC via TCP (default: unset)
+`CARDANO_NODE_PORT` - Port to Cardano node NtC via TCP (default: unset)
+`CARDANO_NODE_NETWORK_MAGIC` - Cardano network magic (default: automatically determined from named network)
+`CARDANO_NODE_SOCKET_PATH` - Socket path to Cardano node NtC via UNIX socket (default: /node-ipc/node.socket)