WIP report-url

Author: apasel422

api.bs

@@ -1985,9 +1985,10 @@ set on a response requesting that the user agent invoke the
 <a method for=Attribution>measureConversion()</a> API.
 
 <div class=example id=ex-measure-conversion-header>
-This is the HTTP equivalent of <a href=#ex-measure-conversion>the JavaScript `measureConversion` example</a>:
+This is the HTTP equivalent of <a href=#ex-measure-conversion>the JavaScript `measureConversion` example</a>,
+with the addition of a `report-url` to which the resulting report will be `POST`ed:
 <xmp highlight=http>
-Measure-Conversion: aggregation-service="https://aggregator.example/tee", histogram-size=20, epsilon=1.0, lookback-days=14, impression-sites=("publisher.example" "other.example"), impression-callers=("ad-tech.example"), match-values=(2), credit=(0.25 0.25 0.5), value=3, max-value=7
+Measure-Conversion: aggregation-service="https://aggregator.example/tee", histogram-size=20, epsilon=1.0, lookback-days=14, impression-sites=("publisher.example" "other.example"), impression-callers=("ad-tech.example"), match-values=(2), credit=(0.25 0.25 0.5), value=3, max-value=7, report-url="https://report-handler.example/foo"
 </xmp>
 </div>
 
@@ -2056,13 +2057,18 @@ optional keys are populated the same way as the corresponding
     Value of <a dict-member for=AttributionConversionOptions>maxValue</a>,
     a positive [=structured header/integer=]. This key is optional.
   </dd>
+  <dt><dfn noexport><code>report-url</code></dfn></dt>
+  <dd>
+    A [=structured header/string=] containing the [=potentially trustworthy URL=]
+    to which the resulting report, if any, will be `POST`ed. The URL may be
+    relative to the request URL, and its [=url/scheme=] must be "`http`" or "`https`".
+    This key is required.
+  </dd>
 </dl>
 
-Issue: Add a required field indicating where to send the resulting report.
-
 <div algorithm>
 To <dfn noexport>parse a `Measure-Conversion` header</dfn> given a [=header value=]
-|input|, run these steps:
+|input| and [=URL=] |baseUrl|, run these steps:
 
 1.  Let |dict| be the result of [=structured header/parsing structured fields=]
     with <var ignore>input_bytes</var> set to |input| and
@@ -2072,6 +2078,12 @@ To <dfn noexport>parse a `Measure-Conversion` header</dfn> given a [=header valu
 1.  If |aggregationService| is not a [=structured header/string=], return an error.
 1.  Let |histogramSize| be |dict|["<code>[=measure-conversion/histogram-size=]</code>"] [=map/with default=] `undefined`.
 1.  If |histogramSize| is not a positive [=structured header/integer=], return an error.
+1.  Let |reportUrlString| be |dict|["<code>[=measure-conversion/report-url=]</code>"] [=map/with default=] `undefined`.
+1.  If |reportUrlString| is not a [=structured header/string=], return an error.
+1.  Let |reportUrl| be the result of applying the [=URL parser=] to |reportUrlString|, with |baseUrl|.
+1.  If |reportUrl| is failure, return an error.
+1.  If |reportUrl| is not a [=potentially trustworthy URL=], return an error.
+1.  If |reportUrl|'s [=url/scheme=] is not "`http`" or "`https`", return an error.
 1.  Let |opts| be a new {{AttributionConversionOptions}} with the following items:
      : {{AttributionConversionOptions/aggregationService}}
      :: |aggregationService|
@@ -2117,7 +2129,7 @@ To <dfn noexport>parse a `Measure-Conversion` header</dfn> given a [=header valu
      1.  Let |maxValue| be its [=map/value=].
      1.  If |maxValue| is not a positive [=structured header/integer=], return an error.
      1.  Set |opts|.{{AttributionConversionOptions/maxValue}} to |maxValue|.
-1.  Return |opts|.
+1.  Return (|opts|, |reportUrl|).
 
 </div>