Map columns by header, not by letterColumn C is a rumor. The moment a client inserts "Middle Name" between A and B, every hard-coded letter in your script writes into the wrong…
Build a Header → Column Index MapHard-coding column letters (C, D) breaks the moment a client inserts a column. Build a { headerName: columnIndex } map once from row 1, then…
Ensure Header Row ExistsImporters and upserts assume row 1 is headers. Empty tabs and "someone deleted column C" both break that. This helper creates the header row…
