[2022-12] Add a note to CoerceArgumentValues linking back to IsVariableUsageAllowed note

[benjie]

Relates to graphql/graphql-spec#1002

Validation note: http://spec.graphql.org/draft/#sec-All-Variable-Usages-Are-Allowed.Allowing-Optional-Variables-When-Default-Values-Exist

Relevant algorithm: http://spec.graphql.org/draft/#CoerceArgumentValues() (specifically 5.j.iii.1)

Timestamped video link: https://youtu.be/nkPn-F_UBJo?list=PLP1igyLx8foH30_sDnEZnxV_8pYW3SDtb&t=3378

• assignee(s): @benjie
• source: https://github.com/graphql/graphql-wg/blob/main/notes/2022/2022-12.md#field-error-resulting-from-insufficient-validation-of-variables-15m-benjie

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Note: Action Item issues are reviewed and closed during Working Group
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[benjie]

I realised after this call that my original issue was indeed legitimate and we'd gotten a little confused on the call and thought I was talking about an argument being a variable, when what I was talking about was a list item being a variable.

I've addressed this by raising a clarifying PR here: graphql/graphql-spec#1058

[benjie]

PR raised to RFC1; closing