Merge branch 'rpc-authentication' into 'dev'

Add rpc authentication configuration

See merge request ergo/rosen-bridge/operation!36

docs/watcher/deploy-docker.md

@@ -305,7 +305,9 @@ As a Bitcoin watcher, you should specify these configurations under `bitcoin` ke
 ```yaml
 type: rpc
 rpc:
-  url: YOUR_RPC_URL
+  url: 'YOUR_RPC_URL'
+  username: 'YOUR_RPC_USERNAME'
+  password: 'YOUR_RPC_PASSWORD'
 ```
 
 or
@@ -318,6 +320,8 @@ esplora:
 
 > Note: If you don't specify an esplora url, it will use the https://blockstream.info by default, but in case you're using RPC as your source you should specify your bitcoin node instance RPC url.
 
+> Note: RPC authentication configuration is optional, if you're using a public node you don't need to add username and password.
+
 > Note: You can use both configuration, but using RPC is recommended. An RPC connection to a bitcoin node is much faster and does not have limits on fetching data.
 
 2. Set your watcher's initial height, where you start observing and reporting events. Like the Ergo network, we highly recommend using the latest block as your initial point. You should specify the initial block height.
@@ -356,6 +360,8 @@ bitcoin:
   type: rpc
   rpc:
     url: 'YOUR_BITCOIN_RPC_URL'
+    username: 'YOUR_RPC_USERNAME'
+    password: 'YOUR_RPC_PASSWORD'
   initial:
     height: LATEST_BITCOIN_HEIGHT
 observation: