docs(readme): initial usage documentation (#184)

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

Author: wolf31o2

README.md

@@ -1,2 +1,105 @@
 # tx-submit-api-mirror
-Simple cardano-submit-api look-alike that mirrors requests asynchronously to configured backends
+
+A simple Cardano transaction submission API service which mirrors all incoming
+requests asynchronously to configured backend submission API services.
+
+A simple HTTP API which accepts a CBOR encoded Cardano transaction as a
+payload body and submits it to one or more configured backend transaction
+submission API services.
+
+## Usage
+
+The recommended method of using this application is via the published
+container images or application binaries.
+
+Docker:
+```
+docker run -e BACKENDS=http://tx1,http://tx2 -p 8090:8090 ghcr.io/blinklabs-io/tx-submit-api-mirror
+docker run -d \
+  -e BACKENDS=http://tx1/api/submit/tx,https://tx2,http://tx3:8090 \
+  -p 8080:8080 \
+  ghcr.io/blinklabs-io/tx-submit-api-mirror
+```
+
+Binaries can be executed directly and are available from
+[Releases](https://github.com/blinklabs-io/tx-submit-api-mirror/releases).
+
+```
+BACKENDS=http://tx1,http://tx2 ./tx-submit-api-mirror
+```
+
+### Configuration
+
+Configuration can be done using either a `config.yaml` file or setting
+environment variables. Our recommendation is environment variables to adhere
+to the 12-factor application philisophy.
+
+#### 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 backend submission APIs.
+
+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)
+- `CLIENT_TIMEOUT` - Timeout for async HTTP operations (default: 60000)
+- `LOGGING_LEVEL` - Logging level for log output (default: info)
+- `TLS_CERT_FILE_PATH` - SSL certificate to use, requires `TLS_KEY_FILE_PATH`
+    (default: empty)
+- `TLS_KEY_FILE_PATH` - SSL certificate key to use (default: empty)
+
+Connection to the backends can be configured using general HTTP Cardano
+transaction submission APIs or using infrastructure providers with a
+transaction submission endpoint. All requests are sent async and non-blocking.
+
+Backends configuration:
+- `BACKENDS` - Comma separated list of HTTP Cardano transaction submission
+    service API URIs
+
+Maestro configuration:
+- `MAESTRO_API_KEY` - API key to a Cardano project on Maestro
+- `MAESTRO_NETWORK` - Named Cardano network to use (default: mainnet)
+- `MAESTRO_TURBO_TX` - Enable use of Maestro TurboTx for transaction submission
+    (default: false)
+
+Connection to Maestro can be performed using specific named network shortcuts
+for known network magic configurations. Supported named networks are:
+
+- mainnet
+- preprod
+- preview
+
+### Sending transactions
+
+This implementation shares an API spec with IOHK's Haskell implementation. The
+same instructions apply. Follow the steps to
+[build and submit a transaction](https://github.com/input-output-hk/cardano-node/tree/master/cardano-submit-api#build-and-submit-a-transaction)
+
+```
+# Submit a binary tx.signed.cbor signed CBOR encoded transaction binary file
+curl -X POST \
+  --header "Content-Type: application/cbor" \
+  --data-binary @tx.signed.cbor \
+  http://localhost:8090/api/submit/tx
+```
+
+## Development
+
+There is a Makefile to provide some simple helpers.
+
+Run from checkout:
+```
+go run .
+```
+
+Create a binary:
+```
+make
+```
+
+Create a docker image:
+```
+make image
+```