Draft: feat(somconnexio): add mail.thread to crm.lead

CHANGELOG:

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- [#nn](https://git.coopdevs.org/coopdevs/som-connexio/odoo-somconnexio/-/merge_requests/nn) Example text

Related card: https://trello.com/c/XXXXXXXX/xjksdjflsdfksldfsdfs

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