Microsoft Azure BUDGET $550 USD

have a project (web app) which already uses OAuth2 to allow users to log in with a Google account and grant access to their calendar(s); based on this, the app reads and creates calendar events as needed (the project is a calendaring app). I need to add support for Microsoft account login and accessing Microsoft account calendars, so the project needs to use OAuth2 to access Microsoft Calendar API. For this it seems I have set up an azure tenancy with Azure AD B2C