add user callback override scenario

features/user_callback.feature

@@ -0,0 +1,10 @@
+Feature: Android support
+
+Scenario: User callback override
+    When I run "UserCallbackScenario" with the defaults
+    Then I should receive a request
+    And the request is a valid for the error reporting API
+    And the exception "message" equals "UserCallbackScenario"
+    And the event "user.id" equals "Agent Pink"
+    And the event "user.email" equals "bob@example.com"
+    And the event "user.name" equals "Zebedee"

mazerunner/src/main/java/com/bugsnag/android/mazerunner/scenarios/UserCallbackScenario.kt

@@ -0,0 +1,17 @@
+package com.bugsnag.android.mazerunner.scenarios
+
+import com.bugsnag.android.Bugsnag
+
+/**
+ * Sends a handled exception to Bugsnag, which overrides the default user via a callback
+ */
+internal class UserCallbackScenario : Scenario() {
+
+    override fun run() {
+        Bugsnag.setUser("abc", "user@example.com", "Jake")
+        Bugsnag.notify(generateException(), {
+            it.error?.setUser("Agent Pink", "bob@example.com", "Zebedee")
+        })
+    }
+
+}