refactor: Add comments to mark needed changes

Author: W-A-James

src/operations/execute_operation.ts

@@ -86,6 +86,7 @@ export function executeOperation<
         owner = Symbol();
         session = topology.startSession({ owner, explicit: false });
       } else if (session.hasEnded) {
+        // TODO: Change this out for MongoExpiredSessionError
         return cb(new MongoDriverError('Use of expired sessions is not permitted'));
       }
     } else if (session) {
@@ -127,6 +128,7 @@ function executeWithServerSelection(
 
   if (inTransaction && !readPreference.equals(ReadPreference.primary)) {
     callback(
+      // TODO: Change this out for MongoTransactionError
       new MongoDriverError(
         `Read preference in a transaction must be primary, not: ${readPreference.mode}`
       )
@@ -188,6 +190,7 @@ function executeWithServerSelection(
     session.inTransaction()
   ) {
     callback(
+      // TODO: Change this out for MongoTransactionError
       new MongoDriverError(
         `Read preference in a transaction must be primary, not: ${readPreference.mode}`
       )