Fix plugin validator, fix version urls, clippy lints, additional categories (#421)

src/util/validate.rs

@@ -88,3 +88,15 @@ pub fn validate_deps(
 
     Ok(())
 }
+
+pub fn validate_url(value: &String) -> Result<(), validator::ValidationError> {
+    let url = url::Url::parse(value)
+        .ok()
+        .ok_or_else(|| validator::ValidationError::new("invalid URL"))?;
+
+    if url.scheme() != "https" {
+        return Err(validator::ValidationError::new("URL must be https"));
+    }
+
+    Ok(())
+}