Added scopes parameter to IProvider.GetTokenAsync

Fixes #111

PR Type

What kind of change does this PR introduce?

Feature

What is the current behavior?

Currently, there is no way to request an access token for scopes that were not initially requested during provider construction. This limits the ability to adopt Graph APIs over time, as features are introduced.

// In app startup code:
// The provider is constructed with an initial set of scopes.
string[] initialScopes = new string[] { "User.Read" };
ProviderManager.Instance.GlobalProvider = new WindowsProvider(initialScopes);

// Somewhere else in the app:
// GetTokenAsync can only retrieve a token configured for the scopes created during provider construction.
IProvider provider = ProviderManager.Instance.GlobalProvider;
string token = await provider.GetTokenAsync(silentOnly: false);

What is the new behavior?

The new behavior adds an additional string[] scopes = null parameter to the end of GetTokenAsync. This allows the option of providing a specific set of scopes to request in the access token:

// App startup code, same as before.

// Somewhere else in the app:
// Alternate scopes can now be requested ad hoc.
IProvider provider = ProviderManager.Instance.GlobalProvider;
string[] alternateScopes = new string[] { "Tasks.ReadWrite", "People.Read" };
string token = await provider.GetTokenAsync(false, alternateScopes);

PR Checklist

Please check if your PR fulfills the following requirements:

[x] Tested code with current supported SDKs
[ ] Sample in sample app has been added / updated (for bug fixes / features)
- [ ] Icon has been created (if new sample) following the Thumbnail Style Guide and templates
[ ] Tests for the changes have been added (for bug fixes / features) (if applicable)
[x] Header has been added to all new source files (run build/UpdateHeaders.bat)
[x] Contains NO breaking changes

CommunityToolkit / Graph-Controls