feat: Create payment sessions (#6549)

~~Opening a draft PR to discuss a couple of implementation details that we should align on~~

**What**

Add workflow and API endpoint for creating payment sessions for a payment collection. Endpoint is currently `POST /store/payment-collection/:id/payment-sessions`. I suggested an alternative in a comment below.

Please note, we intentionally do not want to support creating payment sessions in bulk, as this would become a mess when having to manage multiple calls to third-party providers.

packages/core-flows/src/definition/index.ts

@@ -1,6 +1,6 @@
 export * from "./cart"
 export * from "./inventory"
 export * from "./line-item"
+export * from "./payment-collection"
 export * from "./price-list"
 export * from "./product"
-

packages/core-flows/src/definition/payment-collection/index.ts

@@ -0,0 +1,2 @@
+export * from "./steps"
+export * from "./workflows"

packages/core-flows/src/definition/payment-collection/steps/create-payment-session.ts

@@ -0,0 +1,46 @@
+import { ModuleRegistrationName } from "@medusajs/modules-sdk"
+import { IPaymentModuleService, PaymentProviderContext } from "@medusajs/types"
+import { StepResponse, createStep } from "@medusajs/workflows-sdk"
+
+interface StepInput {
+  payment_collection_id: string
+  provider_id: string
+  amount: number
+  currency_code: string
+  context?: PaymentProviderContext
+  data?: Record<string, unknown>
+}
+
+export const createPaymentSessionStepId = "create-payment-session"
+export const createPaymentSessionStep = createStep(
+  createPaymentSessionStepId,
+  async (input: StepInput, { container }) => {
+    const service = container.resolve<IPaymentModuleService>(
+      ModuleRegistrationName.PAYMENT
+    )
+
+    const session = await service.createPaymentSession(
+      input.payment_collection_id,
+      {
+        provider_id: input.provider_id,
+        currency_code: input.currency_code,
+        amount: input.amount,
+        data: input.data ?? {},
+        context: input.context,
+      }
+    )
+
+    return new StepResponse(session, session.id)
+  },
+  async (createdSession, { container }) => {
+    if (!createdSession) {
+      return
+    }
+
+    const service = container.resolve<IPaymentModuleService>(
+      ModuleRegistrationName.PAYMENT
+    )
+
+    await service.deletePaymentSession(createdSession)
+  }
+)

packages/core-flows/src/definition/payment-collection/steps/index.ts

@@ -0,0 +1,3 @@
+export * from "./create-payment-session"
+export * from "./retrieve-payment-collection"
+

packages/core-flows/src/definition/payment-collection/steps/retrieve-payment-collection.ts

@@ -0,0 +1,27 @@
+import { ModuleRegistrationName } from "@medusajs/modules-sdk"
+import {
+  FindConfig,
+  IPaymentModuleService,
+  PaymentCollectionDTO,
+} from "@medusajs/types"
+import { StepResponse, createStep } from "@medusajs/workflows-sdk"
+
+interface StepInput {
+  id: string
+  config?: FindConfig<PaymentCollectionDTO>
+}
+
+export const retrievePaymentCollectionStepId = "retrieve-payment-collection"
+export const retrievePaymentCollectionStep = createStep(
+  retrievePaymentCollectionStepId,
+  async (data: StepInput, { container }) => {
+    const paymentModuleService = container.resolve<IPaymentModuleService>(
+      ModuleRegistrationName.PAYMENT
+    )
+
+    const paymentCollection =
+      await paymentModuleService.retrievePaymentCollection(data.id, data.config)
+
+    return new StepResponse(paymentCollection)
+  }
+)

packages/core-flows/src/definition/payment-collection/workflows/create-payment-session.ts

@@ -0,0 +1,47 @@
+import { PaymentProviderContext, PaymentSessionDTO } from "@medusajs/types"
+import {
+  WorkflowData,
+  createWorkflow,
+  transform,
+} from "@medusajs/workflows-sdk"
+import {
+  createPaymentSessionStep,
+  retrievePaymentCollectionStep,
+} from "../steps"
+
+interface WorkflowInput {
+  payment_collection_id: string
+  provider_id: string
+  data?: Record<string, unknown>
+  context?: PaymentProviderContext
+}
+
+export const createPaymentSessionsWorkflowId = "create-payment-sessions"
+export const createPaymentSessionsWorkflow = createWorkflow(
+  createPaymentSessionsWorkflowId,
+  (input: WorkflowData<WorkflowInput>): WorkflowData<PaymentSessionDTO> => {
+    const paymentCollection = retrievePaymentCollectionStep({
+      id: input.payment_collection_id,
+      config: {
+        select: ["id", "amount", "currency_code"],
+      },
+    })
+
+    const paymentSessionInput = transform(
+      { paymentCollection, input },
+      (data) => {
+        return {
+          payment_collection_id: data.input.payment_collection_id,
+          provider_id: data.input.provider_id,
+          data: data.input.data,
+          context: data.input.context,
+          amount: data.paymentCollection.amount,
+          currency_code: data.paymentCollection.currency_code,
+        }
+      }
+    )
+
+    const created = createPaymentSessionStep(paymentSessionInput)
+    return created
+  }
+)

packages/core-flows/src/definition/payment-collection/workflows/index.ts

@@ -0,0 +1 @@
+export * from "./create-payment-session"