controllers/version: Add the CrateVersionPathExt trait and provide crate_and_version() fn

Since most endpoints don't need all of the columns for `crates` and
`versions`, it would be great to only load the columns we actually need
to make things faster.
This will enable other endpoints to use the function to make a base
query and customize the needed columns.

Author: eth3lbert

src/controllers/version.rs

@@ -80,4 +80,14 @@ mod ext {
             )
             .filter(canon_crate_name(crates::name).eq(canon_crate_name(crate_name)))
     }
+
+    pub trait CrateVersionPathExt {
+        fn crate_and_version(&self) -> crate_and_version_query<'_>;
+    }
+
+    impl CrateVersionPathExt for CrateVersionPath {
+        fn crate_and_version(&self) -> crate_and_version_query<'_> {
+            crate_and_version_query(&self.name, &self.version)
+        }
+    }
 }