feat: Create cart with line items (#6449)

**What**
- Add support for creating a cart with items
- Add endpoint `POST /store/carts/:id/line-items`
- Add `CreateCartWorkflow`
- Add `AddToCartWorkflow`
- Add steps for both workflows

**Testing**
- Endpoints
- Workflows

I would still call this a first iteration, as we are missing a few pieces of the full flow, such as payment sessions, discounts, and taxes.

Co-authored-by: Adrien de Peretti <25098370+adrien2p@users.noreply.github.com>

packages/utils/src/orchestration/symbol.ts

@@ -1,12 +1,18 @@
 export const SymbolMedusaWorkflowComposerContext = Symbol.for(
   "MedusaWorkflowComposerContext"
-)
-export const SymbolInputReference = Symbol.for("WorkflowInputReference")
-export const SymbolWorkflowStep = Symbol.for("WorkflowStep")
-export const SymbolWorkflowHook = Symbol.for("WorkflowHook")
-export const SymbolWorkflowWorkflowData = Symbol.for("WorkflowWorkflowData")
-export const SymbolWorkflowStepResponse = Symbol.for("WorkflowStepResponse")
-export const SymbolWorkflowStepBind = Symbol.for("WorkflowStepBind")
+).toString()
+export const SymbolInputReference = Symbol.for(
+  "WorkflowInputReference"
+).toString()
+export const SymbolWorkflowStep = Symbol.for("WorkflowStep").toString()
+export const SymbolWorkflowHook = Symbol.for("WorkflowHook").toString()
+export const SymbolWorkflowWorkflowData = Symbol.for(
+  "WorkflowWorkflowData"
+).toString()
+export const SymbolWorkflowStepResponse = Symbol.for(
+  "WorkflowStepResponse"
+).toString()
+export const SymbolWorkflowStepBind = Symbol.for("WorkflowStepBind").toString()
 export const SymbolWorkflowStepTransformer = Symbol.for(
   "WorkflowStepTransformer"
-)
+).toString()