Steps to reproduce
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1. Create two partners A and B.
2. Create a shareable record, e.g. a sales order, and set A as the customer.
3. Share the record with B.
4. Use the share link sent to B and comment on the record.
5. Your comments will be sent with A as the author.
Expected behavior
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Share links sent to a customer should make you comment as that customer.
Task-2883044
X-original-commit: df162acc589b74b0e3c1e9687ce6a1980233f5f1
Part-of: odoo/odoo#94695
Vincent Larcin
7a2650760d