Refactor FormLayout.tsx — optimize conditions in update/create completion handlers

[akanshaaa19]

Summary

handleUpdateCompleted (lines 222–261) and handleCreateCompleted (lines 263–296) contain nearly identical conditional logic:

1. Check for errors → delegate to customHandler or setErrorMessage
2. Check isValid === false → set customError
3. Else → run additionalQuery, set link, show notification, call afterSave

Both also share the saveOnPageChange || isSaveClick notification branching and the onSaveClick(false) cleanup.

Suggested approach

• Extract the shared condition tree into a single helper (e.g. handleMutationCompleted) parameterized by the differences (mutation key, notification verb, link-setting logic).
• Simplify the nested if/else if/else chain — consider early returns for error/invalid cases to flatten the nesting.