Global theme and account removal

[mpbw2]

Type of change

• Bug fix
• New feature development
• Tech debt (refactoring, code cleanup, dependency upgrades, etc)
• Build/deploy pipeline (DevOps)
• Other

Objective

• Apply theme selections globally (took this approach so we can restore per-account themes in the future by removing a contained block of code)
• Support for account removal from login page (via logout on vault timeout)
• Check for existing account on add-account and prompt to switch if available

Code changes

• LoginPage.*: Added "Remove Account" menu option and supporting code, also added checking for already-added account when logging in a new account
• OptionsPageViewModel.cs: Apply theme globally when applied in Settings
• StateService.cs: Added GetUserIdAsync and ApplyThemeGloballyAsync methods

Screenshots

Testing requirements

• Change theme then switch users - theme will remain consistent
• Switch to an active logged-out account and expand the overflow menu to use the "Remove Account" option
• Add an account you've already added

Before you submit

• I have added unit tests where it makes sense to do so (encouraged but not required)
• This change requires a documentation update (notify the documentation team)
• This change has particular deployment requirements (notify the DevOps team)

[fedemkr]

Add try...catch

[mpbw2]

Can you clarify? This is triggered directly by the user with the app in the foreground.

[fedemkr]

@mportune-bw if the ShowDialogAsync or the _messagingService throw an exception the app will crash given that the RemoveAccountAsync is called from the event RemoveAccount_Clicked. So a try...catch is needed here or in RemoveAccount_Clicked to prevent the crash if any exception happen.

[fedemkr]

I think we should use the explicit exception here which is ArgumentNullException

[fedemkr]

Given that email can't be null because of aforementioned check, then this can be directly written as
if (accountEmail == email)

[fedemkr]

In order to avoid nesting and some lines, I'd rewrite this as:

if (_state?.Accounts == null)
{
    return;
}

var activeUserId = await GetActiveUserIdAsync();
foreach (var account in _state.Accounts)
{
    var uid = account.Value?.Profile?.UserId;
    if (uid != null && uid != activeUserId)
    {
        // active user theme not already set, so set it
        await SetThemeAsync(value, uid);
    }
}