Propose the deprecation of universal APK generation (#133)

* Input deprecated

* Warn added to the deployment logic

* Warning message updated

* Ship addon hint inclueded in the warning message

* Deprecated added to the name of the input

* Tech writer fixes

main.go

@@ -335,6 +335,10 @@ func findAPKsAndAABs(pths []string) (apks []string, aabs []string, others []stri
 func deploy(clearedFilesToDeploy []string, config Config) (ArtifactURLCollection, error) {
 	apks, aabs, others := findAPKsAndAABs(clearedFilesToDeploy)
 
+	log.Warnf(`Universal APK generation is going to be DEPRECATED with the next major release! In case you build a bundle and you would like to
+export a universal APK to distribute it for testing (by Public install page or Ship Add-on), please use the Export Universal APK Step instead!
+You may find further information about the Step here (https://devcenter.bitrise.io/deploy/android-deploy/exporting-a-universal-apk-from-an-aab/).`)
+
 	if config.GenerateUniversalApkIfNone {
 		var err error
 		apks, _, err = ensureAABsHasUniversalAPKPair(aabs, apks, config.BundletoolVersion)

step.yml

@@ -225,11 +225,15 @@ inputs:
       is_sensitive: true
   - generate_universal_apk_if_none: "true"
     opts:
-      title: "Force generate universal APK for AABs"
+      title: "Force generate universal APK for AABs (DEPRECATED)"
       description: |
+        Universal APK generation is scheduled to be **DEPRECATED** in the next
+        major release. Please use the **Export Universal APK** Step instead! You 
+        may find further information about the Step in our [Exporting a universal APK from an AAB](https://devcenter.bitrise.io/deploy/android-deploy/exporting-a-universal-apk-from-an-aab/) article.
+
         When building an AAB artifact, check for a corresponding universal APK.
         If none is found, generate the corresponding locally (debug) signed
-        universal APK for ease of debugging.
+        universal APK for easier debugging.
   - debug_mode: "false"
     opts: 
       category: Debug