fix manually enabling logic + add tests (#68)

Author: prayansh

core/src/main/java/com/segment/analytics/kotlin/core/Settings.kt

@@ -43,9 +43,6 @@ data class Settings(
 
 internal fun Analytics.update(settings: Settings, type: Plugin.UpdateType) {
     timeline.applyClosure { plugin ->
-        if (plugin is DestinationPlugin) {
-            plugin.enabled = settings.hasIntegrationSettings(plugin)
-        }
         // tell all top level plugins to update.
         // For destination plugins they auto-handle propagation to sub-plugins
         plugin.update(settings, type)

core/src/main/java/com/segment/analytics/kotlin/core/platform/Plugin.kt

@@ -93,7 +93,12 @@ abstract class DestinationPlugin : EventPlugin {
         timeline.remove(plugin)
     }
 
+    /**
+     * Update `enabled` state of destination and apply settings update to destination timeline
+     * We recommend calling `super.update(..., ...) in case this function is overridden
+     */
     override fun update(settings: Settings, type: Plugin.UpdateType) {
+        enabled = settings.hasIntegrationSettings(this)
         // Apply settings update to its own plugins
         timeline.applyClosure {
             it.update(settings, type)

core/src/main/java/com/segment/analytics/kotlin/core/platform/plugins/SegmentDestination.kt

@@ -101,6 +101,7 @@ class SegmentDestination : DestinationPlugin() {
     }
 
     override fun update(settings: Settings, type: Plugin.UpdateType) {
+        super.update(settings, type)
         if (settings.hasIntegrationSettings(this)) {
             settings.destinationSettings<SegmentSettings>(key)?.let {
                 pipeline.apiHost = it.apiHost