**What**
- Implement adding a line item to order (edit)
**How**
- _by implementing the following "flow"_
- generate a line item
- computing line item adjustments for that line item
- creating tax lines
- creating a change record
**Testing**
- **_integration tests_**
- check if line item and order item change objects are created (with correct tax lines)
- line item adjustments are generated if
- fixed discount is applied to cart
- percentage discount is applied
- **_unit tests_**
- ensure that methods from Inventory, LineItem, LineItemAdjustment etc. services are called
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RESOLVES CORE-495
**what**
Support `updateLineItem` which does the following:
- If no item change exist then create a new one and attaches the clone item with the adjustments and tax lines
- if an item change exists then delete/create adjustments and tax lines and update the cloned item quantity
**Tests**
- Unit tests core + client
- integration tests
- When no item change already exists
- When an item change already exists
FIXES CORE-497
**What**
- Improve `retrieveActive` to take into account `(confirmed/canceled/declined)_at`
**Test**
- one more Integration test on that case
FIXES CORE-601
**What**
- Implements the admin create end point
- Service implementation of the create method and the retrieveActive as well as the totals computation
- Improve compute line items
- client
- medusa-js api
- medusa-react mutations hooks
**Tests**
- Unit tests of the create end points
- Unit tests of the service create method
- Integration tests for admin that also take into account totals computations
- client
- medusa-js tests
- medusa-react hooks tests
FIXES CORE-491
**What**
- Implements the admin/store retrieval end point
- Service implementation of the retrieve method
- Service implementation of the computeLineItems method which aggregates the right line item based on the changes that are made
- client
- medusa-js api
- medusa-react queries hooks
**Tests**
- Unit tests of the retrieval end points
- Unit tests of the service retrieve method and computeLineItems
- Integration tests for admin/store
- client
- medusa-js tests
- medusa-react hooks tests
FIXES CORE-492
