Currently, when the creation of an user access is set to `invitation
only` in the website settings, a project shared to a partner with no
user account will not be accessible to that partner. The link sent to
this partner will instead redirect him to the homepage of the website.
This commit address this situation by allowing the partner that receive
the link to create a portal access. The user that share the project is
warned that partners will be able to create user accounts and offered
the option to proceed or not.
task-3356419
closesodoo/odoo#129790
Signed-off-by: Xavier Bol (xbo) <xbo@odoo.com>