Member Subscription Report about membership-system

[naxxfish]

A preliminary version of this is in PR #206 (to dev branch) , although this requires some refining before going live.

[naxxfish]

From @unknowndomain :

Would you also be able to display a table total
Showing how many members have subscription ids
Mandate ids
Total monthly income from all these
And importantly membership active
Or maybe the date it expires

[naxxfish]

This is currently living in naxxfish/member-subs-again

This may actually be two different apps - one of which surely is just an extension of the existing member list view for superadmins to include gocardless information (minimum sub amount, for example) - and the other to provide a summary of all active subscriptions as of this month.

[naxxfish]

For this to progress, we need to have some specific requirements written down - preferably in User Story type format, for example:

"As an Administrator, I want to see the total number of users with an active mandate".
"As an Administrator, I want to see a list of users with member status"

This list may be fulfilled by several reports or sub-apps in the end, but we need this written down somewhere before we can really work on this.