The `target` attribute for a link specifies where that link should open
(for example, in a new tab). Previously, copy-pasting links in the
website editor (within text blocks for example) would remove the
`target` attribute. This implied loss of functionality.
This commit whitelists the `target` attribute to fix that behavior.
task-3184150
closesodoo/odoo#113908
X-original-commit: 1464752aca36198e5fed5dc8f5b5041244e6e4a9
Signed-off-by: David Monjoie (dmo) <dmo@odoo.com>