Add shutdown signal (#238)

* Add shutdown signal handling

Revert periodic sync interval change

Revert keep-alive interval change

CLI: Add disconnect command

SDK: Add scaffolding for is_started, shutdown()

Simplify instance init

* Rebase on savage-async-ws branch

* Avoid waiting when shutdown signal is received in the sync loop

* Directly use shutdown signal in background threads

* Acquire is_started lock at the very beginning of start()

* Fix cargo clippy warnings

* Update RN generator (kt): set bindingLiquidSdk to null on disconnect()

* Update RN generator (swift): set bindingLiquidSdk to nil on disconnect()

* Startup: only run foreground sync() if this could be the first run

* Start a sync() in background, before regular sync() loop

* Remove ensure_started check from start()

* Add bindings for disconnect()

* Remove foreground sync condition from startup

* Simplify background sync loop

packages/react-native/android/src/main/java/com/breezliquidsdk/BreezLiquidSDKModule.kt

@@ -254,4 +254,17 @@ class BreezLiquidSDKModule(reactContext: ReactApplicationContext) : ReactContext
             }
         }
     }
+
+    @ReactMethod
+    fun disconnect(promise: Promise) {
+        executor.execute {
+            try {
+                getBindingLiquidSdk().disconnect()
+                bindingLiquidSdk = null
+                promise.resolve(readableMapOf("status" to "ok"))
+            } catch (e: Exception) {
+                promise.reject(e.javaClass.simpleName.replace("Exception", "Error"), e.message, e)
+            }
+        }
+    }
 }