Add integration tests for nested files (#4754)

Some tests were missing to ensure that files nested within other GraphQL
types still resolved correctly, so this commit addresses that.

Fixes #4709 

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---

**Checklist**

Complete the checklist (and note appropriate exceptions) before the PR
is marked ready-for-review.

- [ ] Changes are compatible[^1]
- [ ] Documentation[^2] completed
- [ ] Performance impact assessed and acceptable
- Tests added and passing[^3]
    - [ ] Unit Tests
    - [x] Integration Tests
    - [ ] Manual Tests

**Exceptions**

*Note any exceptions here*

**Notes**

[^1]: It may be appropriate to bring upcoming changes to the attention
of other (impacted) groups. Please endeavour to do this before seeking
PR approval. The mechanism for doing this will vary considerably, so use
your judgement as to how and when to do this.
[^2]: Configuration is an important part of many changes. Where
applicable please try to document configuration examples.
[^3]: Tick whichever testing boxes are applicable. If you are adding
Manual Tests, please document the manual testing (extensively) in the
Exceptions.

apollo-router/tests/fixtures/file_upload/single_subgraph.graphql → apollo-router/tests/fixtures/file_upload/schema.graphql

@@ -23,11 +23,8 @@ directive @link(url: String, as: String, for: link__Purpose, import: [link__Impo
 scalar join__FieldSet
 
 enum join__Graph {
-  ACCOUNTS @join__graph(name: "accounts", url: "https://accounts.demo.starstuff.dev/")
-  INVENTORY @join__graph(name: "inventory", url: "https://inventory.demo.starstuff.dev/")
-  PRODUCTS @join__graph(name: "products", url: "https://products.demo.starstuff.dev/")
-  REVIEWS @join__graph(name: "reviews", url: "https://reviews.demo.starstuff.dev/")
   UPLOADS @join__graph(name: "uploads", url: "http://127.0.0.1:4005/")
+  UPLOADS_CLONE @join__graph(name: "uploads_clone", url: "http://127.0.0.1:4006/")
 }
 
 scalar link__Import
@@ -44,53 +41,11 @@ enum link__Purpose {
   EXECUTION
 }
 
-type Product
-  @join__type(graph: INVENTORY, key: "upc")
-  @join__type(graph: PRODUCTS, key: "upc")
-  @join__type(graph: REVIEWS, key: "upc")
-{
-  upc: String!
-  weight: Int @join__field(graph: INVENTORY, external: true) @join__field(graph: PRODUCTS)
-  price: Int @join__field(graph: INVENTORY, external: true) @join__field(graph: PRODUCTS)
-  inStock: Boolean @join__field(graph: INVENTORY)
-  shippingEstimate: Int @join__field(graph: INVENTORY, requires: "price weight")
-  name: String @join__field(graph: PRODUCTS)
-  reviews: [Review] @join__field(graph: REVIEWS)
-  reviewsForAuthor(authorID: ID!): [Review] @join__field(graph: REVIEWS)
-}
-
-type Query
-  @join__type(graph: ACCOUNTS)
-  @join__type(graph: INVENTORY)
-  @join__type(graph: PRODUCTS)
-  @join__type(graph: REVIEWS)
-{
-  me: User @join__field(graph: ACCOUNTS)
-  topProducts(first: Int = 5): [Product] @join__field(graph: PRODUCTS)
-}
-
-type Review
-  @join__type(graph: REVIEWS, key: "id")
-{
-  id: ID!
-  body: String
-  author: User @join__field(graph: REVIEWS, provides: "username")
-  product: Product
-}
-
-type User
-  @join__type(graph: ACCOUNTS, key: "id")
-  @join__type(graph: REVIEWS, key: "id")
-{
-  id: ID!
-  name: String @join__field(graph: ACCOUNTS)
-  username: String @join__field(graph: ACCOUNTS) @join__field(graph: REVIEWS, external: true)
-  reviews: [Review] @join__field(graph: REVIEWS)
-}
-
 
 scalar Upload
   @join__type(graph: UPLOADS)
+scalar UploadClone
+  @join__type(graph: UPLOADS_CLONE)
 
 type File
   @join__type(graph: UPLOADS)
@@ -100,9 +55,34 @@ type File
   encoding: String!
   body: String!
 }
+type FileClone
+  @join__type(graph: UPLOADS_CLONE)
+{
+  filename: String!
+  mimetype: String!
+  encoding: String!
+  body: String!
+}
+
+input NestedUpload
+  @join__type(graph: UPLOADS)
+{
+  file: Upload!
+}
+
+type Query
+  @join__type(graph: UPLOADS)
+  @join__type(graph: UPLOADS_CLONE)
+{
+  empty: String
+}
 
 type Mutation
   @join__type(graph: UPLOADS)
+  @join__type(graph: UPLOADS_CLONE)
 {
   singleUpload(file: Upload): File @join__field(graph: UPLOADS)
+  singleUploadClone(file: UploadClone): FileClone @join__field(graph: UPLOADS_CLONE)
+  multiUpload(files: [Upload!]!): [File!]! @join__field(graph: UPLOADS)
+  nestedUpload(nested: NestedUpload): File @join__field(graph: UPLOADS)
 }