Purpose of this merge is to improve access mode and authentication management
introduced at 9771fdfe8f . Purpose of this cleaning is to simplify options and make
them clearer. Instead of a selection with 4 entries we propose to use two
fields on survey model :
* access_mode: everyone with a public link can access and answer; or only
invited people;
* login required: whether people have to login to answer or not;
All main use cases are covered with combination of those two options.
This commit is linked to task ID 1932508 and PR #30508.
Thibault Delavallée
e65bcb24fd