sqlpage.link: improve error message

Author: lovasoa

src/webserver/database/sqlpage_functions/functions.rs

@@ -396,9 +396,8 @@ async fn link<'a>(
 ) -> anyhow::Result<String> {
     let mut url = file.into_owned();
     if let Some(parameters) = parameters {
-        let encoded = serde_json::from_str::<URLParameters>(&parameters).with_context(|| {
-            format!("link: invalid URL parameters: not a valid json object:\n{parameters}")
-        })?;
+        let encoded = serde_json::from_str::<URLParameters>(&parameters)
+            .with_context(|| format!("sqlpage.link: {parameters:?} is not a valid JSON object. Expected usage: sqlpage.link(filename, json_parameters)"))?;
         encoded.append_to_path(&mut url);
     }
     if let Some(hash) = hash {