### What
Declare `x-codegen` in OAS for Admin routes - S to V.
### Why
We are introducing a new `x-codegen` OpenApi extension, also known as _vendor extension_, in order to help with passing information down to code generators.
In our case, we wish to declare the `method` name that we would expect to call on a client. This mimics our current JS client package.
E.g. `medusaClient.product.list` where `product` is the tag of the route and `list` is the x-codegen.method value.
We are also defining the name of a potential typed object for query parameters. OAS 3.0 does not allow to bundle query parameters under a single definition but it is not uncommon to see API clients handle all query parameters as a single typed object, like our JS client package. With x-codegen.queryParams, a code generator can create a named and typed object to bundle all query parameters for a given route.
E.g. `medusaClient.customer.retrieve(id: string, queryParams: AdminGetCustomerParams)`
### How
Declare `x-codegen` as an object with fields `method` and `queryParams` on all paths.
Match method and queryParams values with equivalent ones from our current JS client package.
### Test
* Ran OAS validator.
* Ran docs build script.
Expect no visible changes to the documentation.
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