Simplify useCustomMutation implementation

[kevinxh]

This is a follow up for the previous PR #2030

This PR simplifies the implementation structure to remove the if/else block that contains some duplicated code:

Before

// this is a higher order function
const callCustomEndpointWithAuth = () => {...}

// this is NOT a higher order function, this creates some inconsistencies in the code
const callCustomEndpointWithBody = () => {...}

if (!apiOptions?.options?.body) {
        return useReactQueryMutation(
            callCustomEndpointWithBody,  
            mutationOptions
        ) as UseMutationResult<TData, TError, MutationVariables>
    } else {
        return useReactQueryMutation<TData, TError, undefined, unknown>(
            callCustomEndpointWithAuth(apiOptions),
            mutationOptions
        ) as UseMutationResult<TData, TError, MutationVariables>
    }

After

const callCustomEndpointWithAuth = () => {...}

        return useReactQueryMutation(
            callCustomEndpointWithAuth(),
            mutationOptions
        ) as UseMutationResult<TData, TError, MutationVariables>

[kevinxh]

The core change is in this line. We update the mutation function to take arguments.

[kevinxh]

this is to support the test case where i need to verify the http header is sent.

[unandyala]

LGTM