[SG-223] Mobile username generator (#2033)

* SG-223 - Changed page title and password title

* SG-223 - Refactored generated field
* Changed position of generated field
* Replaced buttons generate and copy for icons

* SG-223 - Refactor type to passwordType

* SG-223 - Added password or username selector
* Added string for label type selection

* SG-223 - Added logic for different types of username
* Added strings of new types

* [SG-223] - Added UI components for different username types
* Added static strings for new labels
* Added viewmodel properties to support username generation and their respective options

* [SG-223] Added control over type picker visibility

* [SG-223] Refactored username entry on add edit page and added generate icon
* Added GenerateUsername command

* [SG-223] - Implemented service for username generation

* [SG-223] - Added support for username generation for item creation flow
* Implemented cache for username options
* Added exception handling for api calls

* [SG-223] - Remove unused code

* [SG-223] - Added a new display field for username generated and respective command
* Added description label for each type of username
* Changed defautl value of username from string.Empty to -

* [SG-223] - Removed some StackLayouts and refactored some controls

* [SG-223] - Refactored properties name

* [SG-223] - Added visibility toggle icon for api keys of forwarded email username types

* [SG-223] - Refactored nested StackLayouts into grids.

* [SG-223] - Refactor and pr fixing

* [SG-223] - Removed string keys from Resolve
- Added static string to resources

* [SG-223] - Refactored Copy_Clicked as AsyncCommand
- Improved exception handling
- Refactored TypeSelected as GeneratorTypeSelected

* [SG-223] - Renamed PasswordFormatter

* [SG-223] - Refactored VM properties to use UsernameGenerationOptions
* Removed LoadUsernameOptions

* [SG-223] - Refactored added pickers to use SelectedItem instead SelectedIndex
* Deleted PickerIndexToBoolConverter as it isn't needed anymore

* [SG-223] -  Refactored and simplified Grid row and column definitions

* [SG-223] - Refactored Command into async command
* Added exception handling and feedback to the user

* [SG-223] - Refactored GeneratorType picker to use Enum GeneratorType instead of string

* [SG-223] - Changed some resource keys

* [SG-223] - Refactor method name

* [SG-223] - Refactored code and added logs for switch default cases

* [SG-223] - Added flag to control visibility when in edit mode

* [SG-223] - Added suffix Parenthesis to keys to prevent future conflicts

* [SG-223] - Refactored multiple methods into one, GetUsernameFromAsync
* Removed unused Extensions from enums

* [SG-223] - Added exception message

* [SG-223] - Added localizable enum values through LocalizableEnumConverter

* [SG-223] - Fixed space between controls

* [SG-223] - Removed unused code and refactored some variables and methods names

* [SG-223] - Removed unused code and refactored constant name to be more elucidative

* [SG-223] - Removed unused variable

src/App/Pages/Vault/CipherAddEditPageViewModel.cs

@@ -84,6 +84,7 @@ namespace Bit.App.Pages
             FieldOptionsCommand = new Command<CipherAddEditPageFieldViewModel>(FieldOptions);
             PasswordPromptHelpCommand = new Command(PasswordPromptHelp);
             CopyCommand = new AsyncCommand(CopyTotpClipboardAsync, onException: ex => _logger.Exception(ex), allowsMultipleExecutions: false);
+            GenerateUsernameCommand = new AsyncCommand(GenerateUsernameAsync, onException: ex => OnGenerateUsernameException(ex), allowsMultipleExecutions: false);
             Uris = new ExtendedObservableCollection<LoginUriView>();
             Fields = new ExtendedObservableCollection<CipherAddEditPageFieldViewModel>();
             Collections = new ExtendedObservableCollection<CollectionViewModel>();
@@ -145,6 +146,7 @@ namespace Bit.App.Pages
         public Command FieldOptionsCommand { get; set; }
         public Command PasswordPromptHelpCommand { get; set; }
         public AsyncCommand CopyCommand { get; set; }
+        public AsyncCommand GenerateUsernameCommand { get; set; }
         public string CipherId { get; set; }
         public string OrganizationId { get; set; }
         public string FolderId { get; set; }
@@ -592,6 +594,30 @@ namespace Bit.App.Pages
             await Page.Navigation.PushModalAsync(new NavigationPage(page));
         }
 
+        public async Task GenerateUsernameAsync()
+        {
+            if (!string.IsNullOrWhiteSpace(Cipher?.Login?.Username)
+                && !await _platformUtilsService.ShowDialogAsync(AppResources.AreYouSureYouWantToOverwriteTheCurrentUsername, null, AppResources.Yes, AppResources.No))
+            {
+                return;
+            }
+
+            var page = new GeneratorPage(false, async (username) =>
+            {
+                try
+                {
+                    Cipher.Login.Username = username;
+                    TriggerCipherChanged();
+                    await Page.Navigation.PopModalAsync();
+                }
+                catch (Exception ex)
+                {
+                    OnGenerateUsernameException(ex);
+                }
+            }, isUsernameGenerator: true, emailWebsite: Cipher?.Name, editMode: true);
+            await Page.Navigation.PushModalAsync(new NavigationPage(page));
+        }
+
         public async void UriOptions(LoginUriView uri)
         {
             if (!(Page as CipherAddEditPage).DoOnce())
@@ -838,6 +864,12 @@ namespace Bit.App.Pages
                 _logger.Exception(ex);
             }
         }
+
+        private async void OnGenerateUsernameException(Exception ex)
+        {
+            _logger.Exception(ex);
+            await Page.DisplayAlert(AppResources.AnErrorHasOccurred, AppResources.GenericErrorMessage, AppResources.Ok);
+        }
     }
 
     public class CipherAddEditPageFieldViewModel : ExtendedViewModel