Add very basic support for Stripe subscriptions.
* src/commands.c (cmd_chargecard): Support recurring payments. (cmd_checkamount): Ditto. * src/currency.c (valid_recur_p): New. * src/stripe.c (stripe_find_create_plan): New. (stripe_create_subscription): New.
Example
$ socat - unix-client:/var/run/payproc-test/daemon CHARGECARD Currency: USD Amount: 15 Recur: 12 Desc: Monthly GnuPG donation of 15 USD Stmt-Desc: GnuPG donation Meta[name]: my test donor Email: joe@example.org Card-Token: tok_1AHbsp23ctCHxH4kh26K7jrY OK Email: joe@example.org Meta[name]: my test donor Stmt-Desc: GnuPG donation Desc: Monthly GnuPG Donation of 15 USD Recur: 12 Amount: 15.00 Currency: USD