Update fastlane script to work with Play App Signing (#4986)

Task/Issue URL:
https://app.asana.com/0/1202552961248957/1208202742960277/f

### Description

This PR updates fastlane script to use App Bundle format when uploading
app to the Play Store

### Steps to test this PR

QA-Optional

### No UI changes

app/build.gradle

@@ -88,7 +88,30 @@ android {
                 }
             }
         }
-        release
+        release {
+            def propertiesPath = "${CI_HOME_DIR}/ddg_android_build.properties"
+            def propertiesFile = new File(propertiesPath)
+            if (propertiesFile.exists()) {
+                def props = new Properties()
+                props.load(new FileInputStream(propertiesFile))
+                storeFile = file("${CI_HOME_DIR}/${props['key.store']}")
+                storePassword = props['key.store.password']
+                keyAlias = props['key.alias']
+                keyPassword = props['key.alias.password']
+            }
+        }
+        upload {
+            def propertiesPath = "${CI_HOME_DIR}/ddg_android_build_upload.properties"
+            def propertiesFile = new File(propertiesPath)
+            if (propertiesFile.exists()) {
+                def props = new Properties()
+                props.load(new FileInputStream(propertiesFile))
+                storeFile = file("${CI_HOME_DIR}/${props['key.store']}")
+                storePassword = props['key.store.password']
+                keyAlias = props['key.alias']
+                keyPassword = props['key.alias.password']
+            }
+        }
     }
     buildTypes {
         debug {
@@ -102,11 +125,19 @@ android {
         release {
             minifyEnabled false
             proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
-            signingConfig signingConfigs.release
             manifestPlaceholders = [
                     appIcon     : "@mipmap/ic_launcher_red",
                     appIconRound: "@mipmap/ic_launcher_red_round"
             ]
+
+            if (project.hasProperty('useUploadSigning')) {
+                signingConfig = signingConfigs.upload
+            } else if (isValidSigningConfig(signingConfigs.release)) {
+                signingConfig = signingConfigs.release
+            } else {
+                println "Signing properties not found, release artifacts will not be signed."
+                signingConfig = null
+            }
         }
     }
     flavorDimensions "store"
@@ -137,20 +168,14 @@ android {
         unitTests.returnDefaultValues = true
         animationsDisabled = true
     }
+}
 
-    def propertiesPath = "${CI_HOME_DIR}/ddg_android_build.properties"
-    def propertiesFile = new File(propertiesPath)
-    if (propertiesFile.exists()) {
-        def props = new Properties()
-        props.load(new FileInputStream(propertiesFile))
-        android.signingConfigs.release.storeFile = file("${CI_HOME_DIR}/${props['key.store']}")
-        android.signingConfigs.release.storePassword = props['key.store.password']
-        android.signingConfigs.release.keyAlias = props['key.alias']
-        android.signingConfigs.release.keyPassword = props['key.alias.password']
-    } else {
-        println "Signing properties not found at ${propertiesPath}, releases will NOT succeed"
-        android.buildTypes.release.signingConfig = null
-    }
+static def isValidSigningConfig(signingConfig) {
+    return signingConfig != null &&
+            signingConfig.storeFile?.exists() &&
+            signingConfig.storePassword &&
+            signingConfig.keyAlias &&
+            signingConfig.keyPassword
 }
 
 fulladleModuleConfig {

fastlane/Fastfile

@@ -52,18 +52,18 @@ platform :android do
     end
 
 
-  desc "Upload APK to Play Store, in production track with a very small rollout percentage"
+  desc "Upload AAB to Play Store, in production track with a very small rollout percentage"
   lane :deploy_playstore do
 
     props = property_file_read(file: "app/version/version.properties")
     version = props["VERSION"]
     flversion = convert_version(release_number: version)
-    apkPath = "app/build/outputs/apk/play/release/duckduckgo-#{version}-play-release.apk"
+    aabPath = "app/build/outputs/bundle/playRelease/duckduckgo-#{version}-play-release.aab"
 
     update_fastlane_release_notes(release_number: flversion)
 
     upload_to_play_store(
-      apk: apkPath,
+      aab: aabPath,
       track: 'production',
       rollout: '0.000001', # ie. 0.0001%
       skip_upload_screenshots: true,
@@ -160,20 +160,20 @@ platform :android do
 
       props = property_file_read(file: "app/version/version.properties")
       version = props["VERSION"]
-      apkPath = "app/build/outputs/apk/play/release/duckduckgo-#{version}-play-release.apk"
+      aabPath = "app/build/outputs/bundle/playRelease/duckduckgo-#{version}-play-release.aab"
 
       upload_to_play_store_internal_app_sharing(
-        apk: apkPath
+        aab: aabPath
       )
 
  end
 
  desc "Upload APK to Play Store internal testing track"
  lane :deploy_dogfood do |options|
 
-   UI.message("Apk path: #{options[:apk_path]}")
+   UI.message("Aab path: #{options[:aab_path]}")
    upload_to_play_store(
-     apk: options[:apk_path],
+     aab: options[:aab_path],
      track: 'internal',
      skip_upload_screenshots: true,
      skip_upload_images: true,
@@ -193,6 +193,11 @@ platform :android do
 
     UI.message ("Upload new app version to GitHub\nVersion: #{version}\nRelease Notes:\n=====\n#{releaseNotes}\n=====\n")
 
+    download_universal_apk_from_google_play(
+        version_code: convert_version(release_number: version),
+        destination: apkPath
+    )
+
     set_github_release(
         repository_name: "DuckDuckGo/Android",
         api_token: token,

fastlane/README.md

@@ -21,7 +21,7 @@ For _fastlane_ installation instructions, see [Installing _fastlane_](https://do
 [bundle exec] fastlane android deploy_playstore
 ```
 
-Upload APK to Play Store, in production track with a very small rollout percentage
+Upload AAB to Play Store, in production track with a very small rollout percentage
 
 ### android update_release_notes_playstore