start implementing a skeleton of the v1 dump reader

dump/src/reader/compat/mod.rs

@@ -0,0 +1,17 @@
+pub mod v2;
+pub mod v3;
+pub mod v4;
+
+/// Parses the v1 version of the Asc ranking rules `asc(price)`and returns the field name.
+pub fn asc_ranking_rule(text: &str) -> Option<&str> {
+    text.split_once("asc(")
+        .and_then(|(_, tail)| tail.rsplit_once(')'))
+        .map(|(field, _)| field)
+}
+
+/// Parses the v1 version of the Desc ranking rules `desc(price)`and returns the field name.
+pub fn desc_ranking_rule(text: &str) -> Option<&str> {
+    text.split_once("desc(")
+        .and_then(|(_, tail)| tail.rsplit_once(')'))
+        .map(|(field, _)| field)
+}