Introduced AcessTokenProviders, moved UserContext to Logic project
Implemented access tokens provision and expiration handling
Resolved CalendarClient-AccessTokensProvider cyclic dependency
Introduced RestClientFactory
Introduced AccessTokenProviderFactory
Moved IRestClient from _Core folder to parent folder
Renamed RestClient to RestClientBase, moved it to parent folder
Resolved RestClientFactory cyclic dependency (introduced DependencyResolver)
Fixed saving User data by CalendarAccessTokenExpirationHandler
Merge branch 'authorization_providers_introduction'