GraphQL Armor Max-Depth Plugin Bypass via fragment caching

Summary

### Summary A query depth restriction using the max-depth can be bypassed if `ignoreIntrospection` is enabled (which is the default configuration) by naming your query/fragment `__schema`.

### Details In the `countDepth` function, we have the following code that calculates the depth of a used fragment:

```typescript } else if (node.kind == Kind.FRAGMENT_SPREAD) { if (this.visitedFragments.has(node.name.value)) { return this.visitedFragments.get(node.name.value) ?? 0; } else { this.visitedFragments.set(node.name.value, -1); } const fragment = this.context.getFragment(node.name.value); if (fragment) { let fragmentDepth; if (this.config.flattenFragments) { fragmentDepth = this.countDepth(fragment, parentDepth); } else { fragmentDepth = this.countDepth(fragment, parentDepth + 1); } depth = Math.max(depth, fragmentDepth); if (this.visitedFragments.get(node.name.value) === -1) { this.visitedFragments.set(node.name.value, fragmentDepth); } } } ```

which will calculate the depth of the fragment used in the current node, store the value in `this.visitedFragments` and re-use it in the future to avoid re-calculating the depth for the same fragment.

The issue arises when the same fragment is used multiple times, **at different depths**. The current caching takes into account the depth of the first occurrence, which means if the fragment is re-used later in a higher depth, this cached value is not updated.

So, for example, sending the following query with a max depth of `6`:

```graphql query { books { author { ...Test } } books { author { books { author { ...Test } } } } } fragment Test on Author { books { title } } ```

The first use of `Test` fragment does not exceed the defined limit, and this depth will be cached.

In the second use, the fragment is reused in a greater depth, but the `countDepth` function will still use the depth cached, without accounting for the increased depth.

### PoC

Max depth: `6`

```graphql query { books { author { ...Test } } books { author { books { author { ...Test } } } } } fragment Test on Author { books { title } } ```

### Impact

This issue affects applications using the GraphQL Armor Depth Limit plugin.

### Fix

This is fixed in [PR#824](https://github.com/Escape-Technologies/graphql-armor/pull/824). We now store only the additional depth contributed by the fragment and add it to the parent depth where the fragment is used (`parentDepth`).