Kostia, membership plugin is connected to Oxwall's user roles feature.
User roles control whether users can do certain action or not. For
example: our "Free" role doesn't allow to add any content on the site,
and "VIP" role allows to do everything.
To purchase membership for credits, user needs to earn credits first.
To earn credits he needs to make certain action ( ex. add photo or video).
To make the action user needs to get a user role that allows to do those actions ( in our case VIP role).
To get the user role user needs to purchase the membership.
To purchase membership for credits, user needs to earn credits first.
As you can see we will end up in neverending circle.
That
is why User credits plugin is connected directly with actions. User can
earn or lose credits for actions. When user is losing credits for
adding a blog, for example, it is the same as he would have purchased
ability to add blogs, since when user doesn't have enough credits to
complete certain action, he will be asked to purchase them.