fix(gate): struct typecheck codegen (#983)

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<!-- 1. Explain WHAT the change is about -->

- Fixup for #980

<!-- 3. Explain HOW users should update their code -->

#### Migration notes

---

- [x] The change comes with new or modified tests
- [ ] Hard-to-understand functions have explanatory comments
- [ ] End-user documentation is updated to reflect the change


<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

- **New Features**
- Enhanced object validation now accepts additional properties when
allowed, offering more flexible data processing.
- Introduced a new REST endpoint that returns structured, stringified
data based on provided input.

- **Tests**
- Added a test case to verify the functionality of the new REST endpoint
and ensure robust input validation.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Author: luckasRanarison

src/typegate/src/engine/typecheck/code_generator.ts

@@ -229,10 +229,12 @@ export class CodeGenerator {
       );
     }
 
-    this.validation(
-      "keys.size > 0",
-      `\`unexpected fields: \${[...keys].join(', ')}\``,
-    );
+    if (!typeNode.additionalProps) {
+      this.validation(
+        "keys.size > 0",
+        `\`unexpected fields: \${[...keys].join(', ')}\``,
+      );
+    }
     this.line("}");
     return Object.values(typeNode.properties);
   }

tests/typecheck/input_validator_test.ts

@@ -1,7 +1,7 @@
 // Copyright Metatype OÜ, licensed under the Mozilla Public License Version 2.0.
 // SPDX-License-Identifier: MPL-2.0
 
-import { gql, Meta } from "../utils/mod.ts";
+import { gql, Meta, rest } from "../utils/mod.ts";
 
 import { Type } from "@metatype/typegate/typegraph/type_node.ts";
 import { InputValidationCompiler } from "@metatype/typegate/engine/typecheck/input.ts";
@@ -252,4 +252,13 @@ Meta.test("input validator compiler", async (t) => {
       })
       .on(e);
   });
+
+  await t.should("pass for any struct (rest)", async () => {
+    await rest
+      .get('stringifyStruct?params={"key":"value"}')
+      .expectBody((body) => {
+        assert(typeof body.stringifyStruct === "string");
+      })
+      .on(e);
+  });
 });

tests/typecheck/typecheck.py

@@ -107,11 +107,22 @@ def typecheck(g: Graph):
     empty = t.struct({}).rename("WillNotHaveAnyEffectLikeOtherScalars")
 
     stringify_struct = deno.func(
-        t.struct({"params": t.struct({}, additional_props=True, name="params")}),
+        t.struct(
+            {"params": t.struct({}, additional_props=True, name="params")},
+            name="struct_params",
+        ),
         t.string(),
         code="({params}) => JSON.stringify(params)",
     )
 
+    g.rest(
+        """
+        query stringifyStruct($params: struct_params!) {
+            stringifyStruct(params: $params)
+        }
+        """
+    )
+
     g.expose(
         my_policy,
         createUser=create_user,