Allow Additional Memberships (Add Ons)

Allow creation of additional membership options e.g Personal Training Memberships that could be offer separately and purchases and run along side the existing memberships.

Add on memberships could be offer in the purchase flow as up-sell options if set.

e.g. a member could buy Unlimited Tanning for an extra $8/month, and perhaps a locker for $4/month

Note in the case of shared membership - this improvement could allow for shared members to also separately purchase a membership / add on.