Implement the new fields for citation.

src/types/object.rs

@@ -224,6 +224,8 @@ pub struct Citation<'s> {
     pub prefix: Vec<Object<'s>>,
     pub suffix: Vec<Object<'s>>,
     pub children: Vec<CitationReference<'s>>,
+    pub contents: &'s str,
+    pub post_blank: Option<&'s str>,
 }
 
 #[derive(Debug)]
@@ -832,11 +834,15 @@ impl<'s> StandardProperties<'s> for Citation<'s> {
     }
 
     fn get_contents<'b>(&'b self) -> Option<&'s str> {
-        todo!()
+        Some(self.contents)
     }
 
     fn get_post_blank(&self) -> PostBlank {
-        todo!()
+        self.post_blank
+            .map(|text| text.chars().count())
+            .unwrap_or(0)
+            .try_into()
+            .expect("Too much post-blank to fit into a PostBlank.")
     }
 }
 
@@ -846,11 +852,11 @@ impl<'s> StandardProperties<'s> for CitationReference<'s> {
     }
 
     fn get_contents<'b>(&'b self) -> Option<&'s str> {
-        todo!()
+        None
     }
 
     fn get_post_blank(&self) -> PostBlank {
-        todo!()
+        0
     }
 }