feat: return nicer errors on invalid mod.json and missing loader version

Author: matcool

src/types/mod_json.rs

@@ -159,7 +159,7 @@ impl ModJson {
             Ok(j) => j,
             Err(e) => {
                 log::error!("{}", e);
-                return Err(ApiError::BadRequest("Invalid mod.json".to_string()));
+                return Err(ApiError::BadRequest(format!("Invalid mod.json: {e}")));
             }
         };
         json.version = json.version.trim_start_matches('v').to_string();

src/types/models/loader_version.rs

@@ -170,7 +170,7 @@ impl LoaderVersion {
 			.await
 		{
 			Ok(Some(r)) => Ok(r.into_loader_version()),
-			Ok(None) => Err(ApiError::NotFound("".to_string())),
+			Ok(None) => Err(ApiError::NotFound(format!("Loader version \"{tag}\" not found"))),
 			Err(e) => {
 					log::error!("{:?}", e);
 					Err(ApiError::DbError)