Migrate EnvironmentUrlsKey to pref storage (#725)

src/App/Services/MobileStorageService.cs

@@ -30,8 +30,15 @@ namespace Bit.App.Services
             Constants.MigratedFromV1AutofillPromptShown,
             Constants.TriedV1Resync,
             Constants.ClearCiphersCacheKey,
+            Constants.EnvironmentUrlsKey,
         };
 
+        private readonly HashSet<string> _migrateToPreferences = new HashSet<string>
+        {
+            Constants.EnvironmentUrlsKey,
+        };
+        private readonly HashSet<string> _haveMigratedToPreferences = new HashSet<string>();
+
         public MobileStorageService(
             IStorageService preferenceStorageService,
             IStorageService liteDbStorageService)
@@ -40,13 +47,28 @@ namespace Bit.App.Services
             _liteDbStorageService = liteDbStorageService;
         }
 
-        public Task<T> GetAsync<T>(string key)
+        public async Task<T> GetAsync<T>(string key)
         {
             if(_preferenceStorageKeys.Contains(key))
             {
-                return _preferencesStorageService.GetAsync<T>(key);
+                var prefValue = await _preferencesStorageService.GetAsync<T>(key);
+                if(prefValue != null || !_migrateToPreferences.Contains(key) ||
+                    _haveMigratedToPreferences.Contains(key))
+                {
+                    return prefValue;
                 }
-            return _liteDbStorageService.GetAsync<T>(key);
+            }
+            var liteDbValue = await _liteDbStorageService.GetAsync<T>(key);
+            if(_migrateToPreferences.Contains(key))
+            {
+                if(liteDbValue != null)
+                {
+                    await _preferencesStorageService.SaveAsync(key, liteDbValue);
+                    await _liteDbStorageService.RemoveAsync(key);
+                }
+                _haveMigratedToPreferences.Add(key);
+            }
+            return liteDbValue;
         }
 
         public Task SaveAsync<T>(string key, T obj)

src/App/Services/PreferencesStorageService.cs

@@ -13,7 +13,8 @@ namespace Bit.App.Services
         private readonly string _sharedName;
         private readonly JsonSerializerSettings _jsonSettings = new JsonSerializerSettings
         {
-            ContractResolver = new CamelCasePropertyNamesContractResolver()
+            ContractResolver = new CamelCasePropertyNamesContractResolver(),
+            NullValueHandling = NullValueHandling.Ignore
         };
 
         public PreferencesStorageService(string sharedName)