feat(orchestration,workflows): pipe oncomplete and workflow preparation (#4697)

* chore: pipe onComplete and workflow preparation step

* changeset

* fix: tests

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Co-authored-by: Adrien de Peretti <adrien.deperetti@gmail.com>
Co-authored-by: Oli Juhl <59018053+olivermrbl@users.noreply.github.com>

.changeset/weak-berries-flow.md

@@ -0,0 +1,6 @@
+---
+"@medusajs/orchestration": minor
+"@medusajs/workflows": minor
+---
+
+Add pipe onComplete callback and preparation function to exportsWorkflow