Add Paystack, Flutterwave, and Hubtel for encounter billing.

Clinics on Pro/Enterprise can connect their own gateway in Integrations and collect card or MoMo on bills with 0% Ladill fee, while cash payments and balance totals stay correct for pending checkouts.

app/Http/Controllers/Api/BillController.php

@@ -58,12 +58,14 @@ class BillController extends Controller
         $this->authorizeAbility($request, 'payments.manage');
         $this->authorizeBill($request, $bill);
 
+        $manualMethods = array_keys(collect(config('care.payment_methods', []))->except(['gateway'])->all());
+
         $payment = $this->bills->recordPayment(
             $bill,
             $this->ownerRef($request),
             $request->validate([
                 'amount_minor' => ['required', 'integer', 'min:1'],
-                'method' => ['required', 'string', 'in:'.implode(',', array_keys(config('care.payment_methods')))],
+                'method' => ['required', 'string', 'in:'.implode(',', $manualMethods)],
                 'reference' => ['nullable', 'string', 'max:100'],
             ]),
             $this->ownerRef($request),