Add local GraphQL Playground for SDL development

This commit introduces a new file `test-playground.mjs`, which sets up a local GraphQL Playground server for testing static schemas. The server runs on http://localhost:4000/graphql and utilizes a static SDL schema along with stub scalars. This tool is intended for development and testing purposes only, not for production use.

Author: DysektAI

test-playground.mjs

@@ -0,0 +1,44 @@
+#!/usr/bin/env node
+
+/*
+  Local GraphQL Playground for static schema (SDL) development/testing.
+  - Runs a standalone server on http://localhost:4000/graphql
+  - Uses only the static SDL (schema-static.mjs) and stub scalars
+  - Does not use dynamic data or production API logic
+  - Useful for viewing schema docs and testing queries against the static schema
+  - Not used in production or deployment
+*/
+
+import http from 'http'
+import { createYoga } from 'graphql-yoga'
+import { makeExecutableSchema } from '@graphql-tools/schema'
+import staticSDL from './schema-static.mjs'
+
+// Stubs for custom scalars referenced in staticSDL
+const stubSDL = `
+  scalar LanguageCode
+  scalar ItemType
+  scalar ItemCategoryName
+  scalar HandbookCategoryName
+`
+
+// Build schema from static SDL and stubs
+const schema = makeExecutableSchema({
+    typeDefs: [staticSDL, stubSDL],
+    resolvers: {},
+})
+
+// Enable GraphiQL at /graphql for local exploration
+const yoga = createYoga({
+    schema,
+    graphiql: true,
+})
+
+// Start HTTP server on port 4000
+const server = http.createServer(yoga)
+const PORT = 4000
+server.listen(PORT, () => {
+    console.log(
+        `🚀 GraphQL Playground running at http://localhost:${PORT}/graphql`
+    )
+})