BUG: Omitted optional args become "" or 0 in upstream variables

### Issue workflow progress <!-- PLEASE DO NOT REMOVE THIS SECTION --> _Progress of the issue based on the [Contributor Workflow](https://github.com/the-guild-org/Stack/blob/master/CONTRIBUTING.md#a-typical-contributor-workflow)_ - [ ] 1. The issue provides a reproduction available on [Github](https://github.com/ardatan/graphql-mesh/tree/master/examples/hello-world), [Stackblitz](https://stackblitz.com/github/ardatan/graphql-mesh/tree/master/examples/hello-world) or [CodeSandbox](https://codesandbox.io/s/github/ardatan/graphql-mesh/tree/master/examples/hello-world) > Make sure to fork this template and run `yarn generate` in the terminal. > > Please make sure Mesh package versions under `package.json` matches yours. - [ ] 2. A failing test has been provided - [ ] 3. A local solution has been provided - [ ] 4. A pull request is pending review --- Hi, I am using Mesh Compose + Hive Gateway. If some values in a GraphQL request are not defined, I get incorrect interpolation, such as channel: "" or filter: "". In Mesh Compose, I’m using the `createPrefixTransform` and `createEncapsulateTransform` transformers. **To Reproduce** Steps to reproduce the behavior 1. Create the supergraph: `npx mesh-compose -o supergraph.graphql` 2. Run Hive Gateway with the generated graph: `npx hive-gateway supergraph` 3. Execute a query via Hive Gateway without providing the optional arguments. **Observed behavior** When I send the query `products(first: 100)`, the upstream receives: { "filter": "", "where": "", "sortBy": "", "last": 0 } **Expected behavior** If an argument is not provided in the GraphQL query, it should be omitted from the upstream request variables. It should not be coerced into an empty string (`""`) or `0`, as this breaks the schema. ## Additional context Problematic part of the generated supergraph: sourceArgs: { filter: "{args.filter}", where: "{args.where}", sortBy: "{args.sortBy}", search: "{args.search}", channel: "{args.channel}", first: "{args.first}", last: "{args.last}" } Has anyone encountered this problem? Is there a workaround?