Support "taas" platform

[maxceem]

When retreiving notifications using endpoint GET https://api.topcoder-dev.com/v5/notifications/list?read=false&platform=connect&per_page=1000 we can filter notifications by the platform https://github.com/topcoder-platform/tc-notifications/blob/dev/src/services/NotificationService.js#L199-L206.

At the moment we only support 2 platforms: connect which retunrs only notification types which start from connect.notification. and community which returns all other notifications.

We need to support 3rd platfrom: taas which would return only notifications with type which stats from taas.notification.. Note, that community should be also updated to return all other notifications which are not connect and not taas.