Sanitize content to avoid Formula Injections on CSV export
During the export in CSV, user content should be sanitized properly by adding a `'`character if the cell is starting with one of the following characters: `=`, `+`, `-` or `@` .
**How to reproduce:**
- create a board
- add a column title or a note with: `=1+1`
- export to CSV
- open it in a spreadsheet, the formula is interpreted in the spreadsheet
Note: we can think that people will be able to notice malicious content when they see the board, but a attacker can "trick" users by masking suspicious content under other notes.
**Reference:**
https://www.contextis.com/resources/blog/comma-separated-vulnerabilities/
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