uses structured field issue #6

Author: sdatspun2

draft-ietf-httpapi-idempotency-key-header.md

@@ -65,20 +65,18 @@ An idempotency key is a unique value generated by the client which the resource
 
 ## Syntax
 
-The `Idempotency-Key` request header field describes
 
+`Idempotency-Key` is an Item Structured Header {{!RFC8941}}. Its value MUST be a String (Section 3.3.3 of {{!RFC8941}}. Its ABNF is:
 
-    Idempotency-Key       = idempotency-key-value
-
-    idempotency-key-value = opaque-value
-    opaque-value          = DQUOTE *idempotencyvalue DQUOTE
-    idempotencyvalue      = %x21 / %x23-7E / obs-text
-           ; VCHAR except double quotes, plus obs-text
+    Idempotency-Key = sf-string
+    sf-string = DQUOTE *chr DQUOTE
+    chr       = unescaped / escaped
+    unescaped = %x20-21 / %x23-5B / %x5D-7E
+    escaped   = "\" ( DQUOTE / "\" )
 
 
 Clients MUST NOT include more than one `Idempotency-Key` header field in the same request.
 
-
 The following example shows an idempotency key using `UUID` {{!RFC4122}}:
 
     Idempotency-Key: "8e03978e-40d5-43e8-bc93-6894a57f9324"
@@ -339,4 +337,3 @@ The rules below are defined in {{!RFC7230}}:
 The authors would like to thank Mark Nottingham for his support for this Internet Draft. We would like to acknowledge that this draft is inspired by Idempotency related patterns described in API documentation of [PayPal](https://github.com/paypal/api-standards/blob/master/patterns.md#idempotency) and [Stripe](https://stripe.com/docs/idempotency) as well as Internet Draft on [POST Once Exactly](https://tools.ietf.org/html/draft-nottingham-http-poe-00) authored by Mark Nottingham.
 
 The authors take all responsibility for errors and omissions.
-