Typst template: use content rather than string...

...for title, author, date, email.

Fixes #9823 (escaped `\@` in rendered email).
Allows formatting in title, author, date, and email fields.
Since the PDF metadata requires a string, and typst only
converts the title to a string (not the authors), we use
a small function content-to-string to do this conversion.
Background: typst/typst#2196

data/templates/default.typst

@@ -31,11 +31,11 @@ $if(author)$
   authors: (
 $for(author)$
 $if(author.name)$
-    ( name: "$author.name$",
-      affiliation: "$author.affiliation$",
-      email: "$author.email$" ),
+    ( name: [$author.name$],
+      affiliation: [$author.affiliation$],
+      email: [$author.email$] ),
 $else$
-    ( name: "$author$",
+    ( name: [$author$],
       affiliation: "",
       email: "" ),
 $endif$
@@ -46,7 +46,7 @@ $if(keywords)$
   keywords: ($for(keywords)$$keyword$$sep$,$endfor$),
 $endif$
 $if(date)$
-  date: "$date$",
+  date: [$date$],
 $endif$
 $if(lang)$
   lang: "$lang$",

data/templates/template.typst

@@ -1,3 +1,14 @@
+#let content-to-string(content) = {
+  if content.has("text") {
+    content.text
+  } else if content.has("children") {
+    content.children.map(to-string).join("")
+  } else if content.has("body") {
+    content-to-string(content.body)
+  } else if content == [ ] {
+    " "
+  }
+}
 #let conf(
   title: none,
   subtitle: none,
@@ -17,7 +28,7 @@
 ) = {
   set document(
     title: title,
-    author: authors.map(author => author.name),
+    author: authors.map(author => content-to-string(author.name)),
     keywords: keywords,
   )
   set page(

test/writer.typst

@@ -20,6 +20,17 @@
   stroke: none
 )
 
+#let content-to-string(content) = {
+  if content.has("text") {
+    content.text
+  } else if content.has("children") {
+    content.children.map(to-string).join("")
+  } else if content.has("body") {
+    content-to-string(content.body)
+  } else if content == [ ] {
+    " "
+  }
+}
 #let conf(
   title: none,
   subtitle: none,
@@ -39,7 +50,7 @@
 ) = {
   set document(
     title: title,
-    author: authors.map(author => author.name),
+    author: authors.map(author => content-to-string(author.name)),
     keywords: keywords,
   )
   set page(
@@ -101,14 +112,14 @@
 #show: doc => conf(
   title: [Pandoc Test Suite],
   authors: (
-    ( name: "John MacFarlane",
+    ( name: [John MacFarlane],
       affiliation: "",
       email: "" ),
-    ( name: "Anonymous",
+    ( name: [Anonymous],
       affiliation: "",
       email: "" ),
     ),
-  date: "July 17, 2006",
+  date: [July 17, 2006],
   cols: 1,
   doc,
 )