Add doc comment

Author: Jamesbarford

database/src/lib.rs

@@ -1039,9 +1039,13 @@ impl BenchmarkRequest {
     }
 }
 
+/// Result of inserting into the database
 #[derive(Debug, Clone, PartialEq)]
 pub enum BenchmarkRequestInsertResult {
+    /// The request was inserted into the database and is a unique instance
     Inserted,
+    /// The request was not inserted into the database as something else already
+    /// existed that clashed with the unique clause
     NothingInserted,
 }