PURPOSE

Improve the Email Marketing tour and onboarding to create a "wow effect" when
users test the app.

SPECIFICATIONS

Create a tour for mass_mailing to let user visit Odoo Email Marketing through
a simple mailing creation flow.

This require the following functional changes

  * by default, if user chooses to contact mailing lists and there is a single
    mailing list available, add it as default value for chosen list;
  * create a master mailing list data containing the admin user so that he can
    easily follow the tour and test the mailing application;

LINKS

Task ID 2194876
Community PR odoo/odoo#48259
Upgrade PR odoo/upgrade#983

Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>

In a previous commit, we removed the use of the 'btn-sm' classes as we
used it everywhere for default-size buttons instead of customizing the
size of those default-size buttons directly.

This commit proves it was even more necessary as the 'btn-xs' class does
not exist anymore in BS4 and we so can use the 'btn-sm' class instead.

- The dropdown structure was simplified, allowing to get rid of the
  3-levels structure induced by <ul/> elements and dropdowns can now
  contain anything. The class 'dropdown-item' is now mandatory for
  each dropdown clickable element. The class 'dropdown-item-text' can
  be used to add same padding and style but without making the element
  have a clickable look.

- Dividers now use the class 'dropdown-divider'

- The way dropdowns are opened and hidden also changed (before the
  'open' class was added on the `.dropdown-menu` parent, now the
  'show' class is added on both the `.dropdown-menu` parent and the
  `.dropdown-menu` itself).

- JS-wise, no click event handlers can be put on `.dropdown-toggle`
  elements anymore (instead, use handlers for dropdown events).

- Carets are automatically put on `.dropdown-toggle` elements, so this
  commit replaces the `.caret` elements with this. This feature was
  possible to disable but would prevent us from adding a caret with
  scss. Also, this simplifies the DOM. The 'o-no-caret' class was also
  introduced to allow using the 'dropdown-toggle' class on non-caret
  elements.

- Also adapt the scss to use $caret-width instead of $caret-width-base

Description of the issue/feature this PR addresses:

Accessibility improvements forbids the use of the syntax
`<i class="fa fa-check"/> Some text`
to create a labelled icon. But, by this, some fonts are changed.

Desired behavior after PR is merged:
The old syntax can be used.

Today, Odoo is really tricky to use without seeing the screen, it must be improved to be usable.

This PR forbid to use labels without a "for" attribute, add some title, rule and aria attributes in HTML. With that, Odoo will be fully usable with a screen reader.


* [IMP] Labels must have a for attribute. Improve accessibility.
* [IMP] Better error message when trying to read a missing cached value
* [FIX] Add some aria-label and title attributes for screen readers.
* [FIX] Template name is not included in the error message in case of SyntaxError in QWeb
* [FIX] Improve the Tour failed at step error message to be more explicit.
* [IMP] Add aria-labels
* [FIX] Add missing aria-label on failing test
* [IMP] aria-hidden means hidden. Fix all bad aria-hidden and hide aria-hidden for all.
* [IMP] Color names on kanban views and many2many tags
* [IMP] Add some checks on views for accessibility.
* [IMP] Add `alt` attribute on `img` tags.
* [IMP] Add aria-label and title on non-described icons
* [IMP] Add button role to widgets with btn class
* [IMP] Translate aria and formatted attributes.
* [IMP] Remove wrong aria-labelledby
* [IMP] Add menu role on dropdowns
* [IMP] Buttons must be focusable
* [IMP] Add aria attributes on progress bars
* [IMP] Improve accessibility of basic widgets
* [IMP] Change main layout to more semantic tags
* [IMP] Add menuitem role when missing
* [IMP] Remove wrong role='presentation'
* [IMP] Improve accessibility of tab panels
* [IMP] Add aria-invalid on invalid fields
* [IMP] Add aria-sort on ordered columns
* [IMP] Add role on alerts
* [IMP] Use dialog role, header, main and footer tags for modals
* [IMP] Add labels on o_status
* [IMP] Improve accessibility of kanban view with feeds and articles
* [IMP] Add alerts in case of new messages
* [IMP] Add widget, navigation or img role to aria-labelled items

When an user starts a new mail template, he is now proposed to upgrade
to enterprise to install mass_mailing_themes.

When there is no content in the mail, the user is now forced to choose
a theme. Once the choice is made, the theme introduces default content
(series of snippet to simplify user edition).

The default images are also changed when the theme is switched. To do
that, JS code was implemented so that on theme switch, all the images
are changed to check for images in the static theme folder or use a
theme related xml_id.

+ Refactore theme data management.

* Remove mass mailing template switching system (lemon, airmail, ...)
and replace it with a theme selector which only toggle a different
class on the body.
* Lint JS files.
* Change the way the editor is overridden by mass_mailing in a more
odoo way (put the JS in assets and check on runtime if it must be
applied.

+ fix editor style
+ remove useless code
+ remove odoo template