TL;DR

Added duplex: 'half' to the fetch request options and explicitly cast to RequestInit type in the dev server middleware.

What changed?

Modified the fetch request configuration in createMiddleware function by:

1. Adding the duplex: 'half' option to the request configuration
2. Adding an explicit type cast to RequestInit to ensure TypeScript compatibility

How to test?

1. Start the development server
2. Verify that API requests from the client to the server work correctly
3. Check that streaming responses (if applicable) function as expected

Why make this change?

This change addresses a potential issue with the Fetch API when handling certain types of requests. The duplex: 'half' option specifies that the request is a "half-duplex" connection, which is necessary for some request types to work correctly with newer Fetch API implementations. The explicit type cast ensures TypeScript doesn't raise errors about the additional property.