Add ADR on using UserNotifier to show user feedback

.idea/detekt.xml

@@ -1,6 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <project version="4">
   <component name="DetektProjectConfiguration">
+    <enableDetekt>true</enableDetekt>
     <enableFormatting>true</enableFormatting>
     <rulesPath>$PROJECT_DIR$/config/detekt/config.yml</rulesPath>
   </component>

docs/0002-use-user-notifier-to-show-user-feedback-from-workers.md

@@ -0,0 +1,35 @@
+# Use UserNotifier component to show user feedback from workers
+
+* Status: Accepted
+* Deciders: Marino, Zorica, Stefanija, Davide, Tomasz, Dimitar
+* Date: 09/02/2021
+
+
+## Context and Problem Statement
+
+Given this app is structured to allow all operations to be performed independently from nework availability,
+most of the business and data logic is somehow wrapped into components that handle the part of waiting for
+network (such as jobs and workers).
+
+Having this logic executed asynchronously, in an undefined moment and in the background, represents a challenge
+when it comes to showing feedback to the user in regards of the operation that was executed.
+
+* We want to have a consistent and reliable way to inform the user of any important event that happened in a background Worker (eg. failed to send)
+* We can't rely on the app's UI existing as each worker's execution time depends on external factors (the app might have been killed by the time they execute)
+* We want the ability to fully unit test that this actions happened
+
+## Considered Options
+
+* Inject an android collaborator to display local push notifications
+* Return feedback to the caller (use case) and allow them to handle it
+* Inject an abstract collaborator that can decide how to display feedback (UserNotifier)
+
+## Decision Outcome
+
+* We choose to rely on a small, simple and abstract `UserNotifier` component
+* This component gets injected in a worker and called when feedback needs to be shown
+* UserNotifier decides how to display feedback, for example through a Push notification or a Snackbar or a Toast
+
+## Consequences
+1. All Workers and Jobs that need to show user-visible feedback should do so through an injected instance of UserNotifier component
+