User Dashboard doesn't have Renewal links for certain memberships

Add a CiviMember setting for "default self-service membership renewal page". This can be used to provide a "renewal" link from the User Dashboard for membership that were entered in the backend (by staff).

— Original Post
Paid memberships that are entered in the backend appear to not have a contribution_page associated with their payment. Free memberships also do not have a civicrm_membership_payment record. As a result, the CRM_Member_Page_UserDashboard::listMemberships() does not create a valid link since CRM_Member_BAO_Membership::getContributionPageId does not return a reasonable value.

It seems to me that there needs to be some renew link provided, especially when there is a single contribution page with that membership type on it, which is likely a common use case. Adding a field under Admin > CiviMember > Membership Types that provides a drop-down of contribution pages is a not very user friendly option. An alternative is to modify the Membership Admin tab under contribution page admin so that every enabled membership type has a new field that indicates that this page is the default renewal page. On save, any membership types included that do not have a different contribution page marked as their default renewal page will have this page set to their default. For any membership types that have both this page and a different page marked as default, a confirmation dialogue will come up to confirm the change.