docs(gateway): extend Request Deduplication page with inbound gateway-level deduplication

[Copilot]

The deduplication page previously only covered outbound (transport-level) deduplication. This adds documentation for the new inbound gateway-level deduplication introduced in graphql-hive/gateway#2179, modelled after the Router's equivalent docs.

Changes

• Restored the original introductory paragraph explaining why deduplication matters
• Restructured the page into two explicit sections: Outbound (enabled by default) and Inbound (disabled by default)
• Added inbound deduplication docs covering:
  • Basic enable flag
  • Default deduplication key composition (method, URL, headers, operation doc, name, variables)
  • Header filtering via shouldIncludeHeader
  • Full key customisation via getDeduplicationKeys
  • Per-request conditional toggling via enabled
  • Limitations: queries only; @defer/@stream excluded

import { defineConfig } from "@graphql-hive/gateway";

export const gatewayConfig = defineConfig({
  inboundInflightRequestDeduplication: {
    // Only factor in the authorization header when building the dedup key
    shouldIncludeHeader: (headerName) => headerName === "authorization",
  },
});

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[Copilot]

Pull request overview

Updates the Hive Gateway “Deduplicate Inflight Requests” documentation to cover the newly introduced inbound (gateway-level) inflight request deduplication, alongside the existing outbound (transport-level) deduplication, clarifying when each applies and how to configure them.

Changes:

• Reintroduces/expands the introduction and reframes the page around two deduplication layers (outbound vs inbound).
• Documents inbound deduplication configuration (enable flag, key composition, header filtering, key customization, per-request enabling).
• Adds a limitations section for inbound deduplication (queries only; excludes @defer/@stream).

Comments suppressed due to low confidence (1)

packages/documentation/content/docs/gateway/other-features/performance/deduplicate-inflight-requests.mdx:30

• The example imports HTTPTransportOptions from @graphql-tools/executor-http as a value import. Elsewhere in these docs (e.g. the gateway v1→v2 migration guide) HTTPTransportOptions is shown as a type import, and it’s imported from @graphql-hive/gateway. To keep examples consistent and avoid potential runtime import issues in TS transpilers that preserve value imports, consider switching this to a type-only import and aligning the import source with the migration guide.

import { defineConfig } from "@graphql-hive/gateway";
import { HTTPTransportOptions } from "@graphql-tools/executor-http";

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[ardatan]

@copilot apply changes based on the comments in this thread

[Copilot]

@copilot apply changes based on the comments in this thread

Applied all three changes from that review thread in commit 3b94821:

1. "in-flight" → "inflight" – consistent with the rest of the Gateway docs.
2. Directionality fix – outbound section now reads "identical requests to the same downstream subgraph service" instead of "same upstream resource".
3. Data-leakage warnings – added before both the shouldIncludeHeader and getDeduplicationKeys sections, calling out the risk of cross-user response sharing when narrowing/replacing the deduplication key.