Feat/manual payment (#318)

What
A dummy payment provider for testing and potentially other relevant use cases like accepting cash payments. Also makes it possible to start server without notification/payment/fulfillment providers.

Why
When setting up a starter project it introduces unnecessary overhead to have to set up an account with a payment provider (e.g. Stripe). Adding a dummy provider will remove friction.

How
Extremely simple wrapper functionality.

packages/medusa/src/loaders/defaults.js

@@ -1,6 +1,36 @@
+const silentResolution = (container, name, logger) => {
+  try {
+    const resolved = container.resolve(name)
+    return resolved
+  } catch (err) {
+    if (err.name !== "AwilixResolutionError") {
+      throw err
+    } else {
+      let identifier
+      switch (name) {
+        case "paymentProviders":
+          identifier = "payment"
+          break
+        case "notificationProviders":
+          identifier = "notification"
+          break
+        case "fulfillmentProviders":
+          identifier = "fulfillment"
+          break
+        default:
+          identifier = name
+      }
+      logger.warn(
+        `You don't have any ${identifier} provider plugins installed. You may want to add one to your project.`
+      )
+    }
+  }
+}
+
 export default async ({ container }) => {
   const storeService = container.resolve("storeService")
   const profileService = container.resolve("shippingProfileService")
+  const logger = container.resolve("logger")
 
   const entityManager = container.resolve("manager")
 
@@ -9,19 +39,28 @@ export default async ({ container }) => {
 
     let payIds
     const pProviderService = container.resolve("paymentProviderService")
-    const payProviders = container.resolve("paymentProviders")
+
+    const payProviders =
+      silentResolution(container, "paymentProviders", logger) || []
+
     payIds = payProviders.map(p => p.getIdentifier())
     await pProviderService.registerInstalledProviders(payIds)
 
     let notiIds
     const nProviderService = container.resolve("notificationService")
-    const notiProviders = container.resolve("notificationProviders")
+
+    const notiProviders =
+      silentResolution(container, "notificationProviders", logger) || []
+
     notiIds = notiProviders.map(p => p.getIdentifier())
     await nProviderService.registerInstalledProviders(notiIds)
 
     let fulfilIds
     const fProviderService = container.resolve("fulfillmentProviderService")
-    const fulfilProviders = container.resolve("fulfillmentProviders")
+
+    const fulfilProviders =
+      silentResolution(container, "fulfillmentProviders", logger) || []
+
     fulfilIds = fulfilProviders.map(p => p.getIdentifier())
     await fProviderService.registerInstalledProviders(fulfilIds)