Fix simple citations by making prefixes and suffixes optional.

src/parser/citation.rs

@@ -29,13 +29,14 @@ use crate::parser::Object;
 
 #[tracing::instrument(ret, level = "debug")]
 pub fn citation<'r, 's>(context: Context<'r, 's>, input: &'s str) -> Res<&'s str, Citation<'s>> {
+    // TODO: Despite being a standard object, citations cannot exist inside the global prefix/suffix for other citations because citations must contain something that matches @key which is forbidden inside the global prefix/suffix. This TODO is to evaluate if its worth putting in an explicit check for this (which can be easily accomplished by checking the output of `get_bracket_depth()`). I suspect its not worth it because I expect, outside of intentionally crafted inputs, this parser will exit immediately inside a citation since it is unlikely to find the "[cite" substring inside a citation global prefix/suffix.
     let (remaining, _) = tag_no_case("[cite")(input)?;
     let (remaining, _) = opt(citestyle)(remaining)?;
     let (remaining, _) = tag(":")(remaining)?;
-    let (remaining, _prefix) = parser_with_context!(global_prefix)(context)(remaining)?;
+    let (remaining, _prefix) = opt(parser_with_context!(global_prefix)(context))(remaining)?;
     let (remaining, _references) =
         many0(parser_with_context!(citation_reference)(context))(remaining)?;
-    let (remaining, _suffix) = parser_with_context!(global_suffix)(context)(remaining)?;
+    let (remaining, _suffix) = opt(parser_with_context!(global_suffix)(context))(remaining)?;
     let (remaining, _) = tag("]")(remaining)?;
     let source = get_consumed(input, remaining);
     Ok((remaining, Citation { source }))