Task #1902306

Purpose
=======

Preliminary cleanup
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survey.question is now also the model used for the survey's pages (with the "is_page" field set to True).
This allows to put all the pages and questions together in a o2m field on the view side and
easily reorganize your survey by dragging the items around.

It also removes one level of encoding by directly having 'Add a page' and 'Add a question'
links on the tree view of questions, enabling a faster encoding.

However, this has the downside of making the code reading a little bit more complicated.
Efforts were made at the model level to create computed fields so that the use of these models
still seems somewhat logical. That means:
- A survey still has "page_ids" (question_and_page_ids filtered on is_page = True)
- These "page_ids" still have question_ids (questions located between this page and the next)
- These "question_ids" still have a "page_id"

That makes the use and display of these information at view and controller levels easier to understand.


Certification
----------------

This commit adds certification capabilities to the survey module.

A certification is a survey with the "certification" flag set to true than can be linked
to a certification email template that contains a certification document (PDF).
This template can be edited by the user in the technical settings to customize the certification email/document.

To be able to implement this certification concept, we also have to add scoring mechanisms to surveys.
survey.questions of type 'simple_choice' and 'multiple_choice' now have scores for the suggested answers.
These question scores allow to compute a global score that is used to determine whether the user has successfully
passed the certification or not.

As additional features, we also have:
- A time limit with an interface timer that limits the test to X minutes
  When reached, the survey is automatically submitted and unregistered (= unsubmitted) answers are not taken into account.
- A limited number of attempts for the survey/certification
  If reached, the user can't take the survey/certification anymore

The 'survey result' layout was adapted accordingly to show the success rate of participants and the correct answers
to the survey questions.


Randomization and survey layout selection
---------------------------------------------------------

The "page" concept is now only present in the user interface.
Surveys are split in "sections" that have two purposes:
- Organizing a (long) survey/certification
- Allow to pick a random questions count for that section (more information here after)

On the user interface, based on the questions_layout field, surveys are displayed:
- On a single page, where sections still appear but are only used as visual separations
- On multiple pages, having one page per section (this matches the previous behavior)
- On multiple pages, having one page per *question*

On top of that page concept, this commit added randomization for the survey questions.
The randomization mechanism will take X questions per section of the survey.
The survey.user_input is initialized with the selected questions to be sure to keep that
set of questions and avoid showing a new set of questions every time the user refreshes the page.
This also allows to easilly go back and know which question we have to show.

Specs
=======
- Create a new survey :
  - Add a description field for the survey

- Options on a survey :
  - Passing score : (sum of all good answers) in %
  - If No scoring => No passing score, no certificate
  - If Scoring with answers => Passing score and can see the answers (can create certificate)
  - If Scoring without answers => Passing score but can't review the answers at the end (can create certificate)
  - for the questions, if "no scoring" selected, can 't see the option "good answer" and "score" on the questions
  - If the 2 others options, can see the options "good answer" and "score" on the questions
  - all the types of questions are available for each option.

- Questions
  - Add the option correct answer on the multiples questions (one or more good answers)

- Certifications
  - If scoring, force "mandatory" for "mutliple choices (1or multiple answers)"
  - On the dashboard => visual information that this specific survey is a certification
  - Time Limit : The student is informed on the home screen of the survey of the time limit.
    The clock start when he clicks on "start survey"
  - Template of the certificate : send email with attachment PDF

- Front-end :
  - Add some margin
  - Replace "Back to survey" with the blue-bar from the portal
  - Add a timer (start when the survey starts)
  - Add a progress bar (number of section and number of question inside the section)

- Analyse of the results :
  - First a global graph with the number of people who''ve participated and passed the test

- Stages of a survey :
  - Remove the stage "Permanent"
  - 3 stages :
    - draft : not on-line but can be tested (with phantom token)
    - In progress : on-line
    - closed : not on-line
  - Who can test a survey : the manager and the user. Add this condition to the phantom token.