Make file path start doc entries optional

Author: abbiemery

src/model/metadata.rs

@@ -50,8 +50,8 @@ pub struct Start {
     pub versions: Versions,
     pub instrument: String,
     pub instrument_session: String,
-    pub data_session_directory: String,
-    pub scan_file: String,
+    pub data_session_directory: Option<String>,
+    pub scan_file: Option<String>,
     pub scan_id: i64,
     pub plan_type: String,
     pub plan_name: String,