Add support for managing attachments

Add a new manager for attachment records (`ir.attachment`) in Odoo.

These are intended to be used for uploading/downloading attachments to/from invoices.
Invoice attachments will then be attached to invoice emails sent out to customers.

The contents of the attachments won't be fetched when querying them from Odoo by default;
instead it is intended that the separate `download` method be used to download the attachment
contents separately. An `upload` method is also available, to provide an easier to use interface
for uploading attachments.

Author: Callum Dickinson

_typos.toml

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+[default.extend-words]
+datas = "datas"

changelog.d/7.added.md

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+Add support for managing attachments