NEBULA-1385: Add initialState to embedable sandbox based on config

docs/source/api/plugin/landing-pages.md

@@ -106,6 +106,52 @@ By default, the landing page displays a footer that links to the documentation t
 <tr>
 <td>
 
+###### `document`
+
+`string`
+</td>
+<td>
+
+A GraphQL document (eg, query or mutation) to populate in the Studio Explorer's editor on load.
+
+If you omit this, the Explorer initially loads an example query based on your schema.
+
+</td>
+</tr>
+
+<tr>
+<td>
+
+###### `variables`
+
+`Record<string, string>`
+</td>
+<td>
+
+An object containing initial variable values to populate in the Explorer on load.
+
+If provided, these variables should apply to the initial query you provide in `document`.
+
+</td>
+</tr>
+
+<tr>
+<td>
+
+###### `headers`
+
+`Record<string, string>`
+</td>
+<td>
+
+An object containing initial HTTP header values to populate in the Explorer on load.
+
+</td>
+</tr>
+
+<tr>
+<td>
+
 ###### `includeCookies`
 
 `boolean`

packages/apollo-server-core/src/plugin/landingPage/default/index.ts

@@ -142,6 +142,11 @@ id="embeddableSandbox"
     target: '#embeddableSandbox',
     initialEndpoint,
     includeCookies: ${config.includeCookies ?? 'false'},
+    initialState: ${JSON.stringify({
+      document: config.document ?? undefined,
+      variables: config.variables ?? undefined,
+      headers: config.headers ?? undefined,
+    })},
   });
 </script>
 `;