chore(orchestration): prevent throwing on already defined workflow (#5337)

**What**
At the moment, when importing something from medusa entry point, if two medusa packages are installed because of a plugin, the evaluation of the import can end up throwing that a workflow is already defined. To prevent that from happening, we can just not throw if it is already defined and just return prematurely and make it idempotent.

packages/orchestration/src/__tests__/workflow/local-workflow.ts

@@ -80,6 +80,52 @@ describe("WorkflowManager", () => {
     expect(wf).toEqual(["create-product", "broken-delivery", "deliver-product"])
   })
 
+  it("should throw when registering a workflow with an existing id", () => {
+    let err
+    try {
+      WorkflowManager.register(
+        "create-product",
+        {
+          action: "foo",
+          next: {
+            action: "bar",
+            next: {
+              action: "xor",
+            },
+          },
+        },
+        handlers
+      )
+    } catch (e) {
+      err = e
+    }
+
+    expect(err).toBeDefined()
+    expect(err.message).toBe(
+      `Workflow with id "create-product" and step definition already exists.`
+    )
+  })
+
+  it("should not throw when registering a workflow with an existing id but identical definition", () => {
+    let err
+    try {
+      WorkflowManager.register(
+        "create-product",
+        {
+          action: "foo",
+          next: {
+            action: "bar",
+          },
+        },
+        handlers
+      )
+    } catch (e) {
+      err = e
+    }
+
+    expect(err).not.toBeDefined()
+  })
+
   it("should begin a transaction and returns its final state", async () => {
     const flow = new LocalWorkflow("create-product", container)
     const transaction = await flow.run("t-id", {

packages/orchestration/src/workflow/workflow-manager.ts

@@ -75,12 +75,18 @@ export class WorkflowManager {
     requiredModules?: Set<string>,
     optionalModules?: Set<string>
   ) {
-    if (WorkflowManager.workflows.has(workflowId)) {
-      throw new Error(`Workflow with id "${workflowId}" is already defined.`)
-    }
-
     const finalFlow = flow instanceof OrchestratorBuilder ? flow.build() : flow
 
+    if (WorkflowManager.workflows.has(workflowId)) {
+      const areStepsEqual =
+        JSON.stringify(finalFlow) ===
+        JSON.stringify(WorkflowManager.workflows.get(workflowId)!.flow_)
+
+      if (!areStepsEqual) {
+        throw new Error(`Workflow with id "${workflowId}" and step definition already exists.`)
+      }
+    }
+
     WorkflowManager.workflows.set(workflowId, {
       id: workflowId,
       flow_: finalFlow,