Feature Request: Config Flag to Enable ID Input Coercion

Section 3.5.5 of the GraphQL spec describes the ID type, and includes following subsection:

Input Coercion

When expected as an input type, any string (such as "4") or integer (such as 4 or -4) input value should be coerced to ID as appropriate for the ID formats a given GraphQL service expects. Any other input value, including float input values (such as 4.0), must raise a request error indicating an incorrect type.

Source

In short: compliant servers should accept a String or Int for ID-type inputs, but it's not required. Unfortunately, Relay has no way to know that a server supports that coercion, so it's forced to limit ID inputs to strings. That's an issue mostly in Flow/TypeScript typings and in the LSP, since Int IDs are disallowed. Clients are then forced to manually stringify Number input IDs at runtime to satisfy that restriction, even though the (generally faster) server supports that cast.

Is there any interest in allowing Relay users to declare server-side support for ID input coercion? I imagine it'd be configurable via a server_supports_id_input_coercion flag (or similar) and default to "off" for safety. It'd be a moderate ergonomics boost for systems that return IDs in Int-typed fields.