Add URL parsing.

src/intermediate/regular_link.rs

@@ -1,4 +1,5 @@
 use organic::types::StandardProperties;
+use url::Url;
 
 use super::macros::intermediate;
 
@@ -46,6 +47,7 @@ pub(crate) enum LinkTarget {
 impl LinkTarget {
     pub(crate) fn from_string<S: AsRef<str>>(input: S) -> Result<LinkTarget, CustomError> {
         fn impl_from_string(input: &str) -> Result<LinkTarget, CustomError> {
+            let parsed = Url::parse(input)?;
             Ok(LinkTarget::Raw(input.to_owned()))
         }
         impl_from_string(input.as_ref())