Problems with automatic renew not checked.

Created by: artfulrobot

As noted in the README:

The "Auto-renew" option is required for the GoCardless payment processor to handle memberships.

If you use Price Sets and you have the "Auto renew option, not required" selected then the user will not be shown the tick-box allowing them to select Auto Renew, and this will break things. So better to use the straight forward auto renew option rather than give an option that will break things.

This issue is caused because it doesn't handle one-off (non auto renewing) payments, and there's some discussion at Issue #12 about this.

Proposal

1. If you select GoCardless as a payment processor, the auto-renew checkbox should be automatically checked.

2. When this happens, a note should show explaining that this is required for paying by Direct Debit.

3. When the payment processor is changed to something else the note should be removed.

4. Manually un-checking the auto renew checkbox should issue a notice saying "nah, can't because Direct Debit" and it should be re-checked!

5. When saving an event form, if the auto-renew is left as optional and a GoCardless processor is used, it should show a warning message.

This all feels messy and confusing, but it might be better than what we have.

Please feed in your thoughts on UX and feel free to suggest other things.