what:
- adds variant inventory link management endpoints:
```
Link inventory item to variant
POST /products/:id/variants/:vid/inventory-items
Update variant's inventory item link
POST /products/:id/variants/:vid/inventory-items/:iid
Unlink variant's inventory item
DELETE /products/:id/variants/:vid/inventory-items/:iid
```
- a batch endpoint that does the above 3 across variants
```
POST /products/:id/variants/inventory-items
```
**What**
- automatically build and consume connection and container loader if not exported by the module
- therefore load the services and repositories automatically, including baseRepository
- automatically build run and revert migrations if not provided
- cleaup modules to remove extra unnecessary bits and pieces
- remove the `initializeFactory` in favor of using `medusaApp`
Should drastically improve the module building DX by removing a lot of boilerplate to handle by the user, that plus the base entity should simplify quite a lot the flow cc @shahednasser
**Note**
I had to choose a way to identify connection and container loader from the exported loader from the module. I decided to go with named function `connectionLoader` and `containerLoader`, also, now the factories will return named function so if the user use the factories we are providing to build those loaders, the function will also be named and identified
