Adds test coverage for a cache issue that could cause edited one-to-many form lines and earlier lines to be lost during change handling. This helps protect data entry workflows in accounting and other forms that rely on multi-line records.

This pull request add a new test about on_change on one2many field.

The method convert_to_cache deletes the line modified and all previous lines from the cache.
The new test fails because of that.

Odoo now avoids using a user's home location for data storage when that home location is not a real directory, such as for system service accounts. This helps deployments start and run more reliably in stricter server setups.

Use site data dir instead of user data dir when user's home is not a directory.
Like system users created with /dev/null as home.

Stricter than before.