[REF] web, *: BS4, use custom BS4 checkbox everywhere

Before this commit, Odoo used checkboxes in three different ways:

- A simple <input type="checkbox"/>, mainly in the frontend. The style
  is browser dependant.

- Same as above but with the BS3, checkbox structure. The style is still
  the same, but the alignement is supposed to be better (which is not
  always the case).

- The Odoo official structure:
	```
	<div class="o_checkbox">
	    <input type="checkbox"/>
	    <span/>
	</div>
	```
  which allows to have a cross-browser checkbox style and correct
  alignements.

The goal after this commit is to only use the BS4 *custom* checkbox
structure to achieve the same goal as our official structure (and
remove that one):

```
<div class="custom-control custom-checkbox">
  <input type="checkbox" class="custom-control-input" id="customCheck1">
  <label class="custom-control-label" for="customCheck1">...</label>
</div>
```

/!\ Labels are now required (use a zero-width space if necessary)

3 files changed, 22 insertions, 7 deletions

diff --git a/addons/web/static/src/js/fields/abstract_field.js b/addons/web/static/src/js/fields/abstract_field.js
index eab0093ed50..7cf72791be5 100644
--- a/addons/web/static/src/js/fields/abstract_field.js
+++ b/addons/web/static/src/js/fields/abstract_field.js
@@ -304,7 +304,6 @@ var AbstractField = Widget.extend({
         this._reset(record, event);
         return this._render() || $.when();
     },
-
     /**
      * Remove the invalid class on a field
      */
@@ -312,7 +311,15 @@ var AbstractField = Widget.extend({
         this.$el.removeClass('o_field_invalid');
         this.$el.removeAttr('aria-invalid');
     },
-
+    /**
+     * Sets the given id on the focusable element of the field and as 'for'
+     * attribute of potential internal labels.
+     *
+     * @param {string} id
+     */
+    setIDForLabel: function (id) {
+        this.getFocusableElement().attr('id', id);
+    },
     /**
      * add the invalid class on a field
      */
@@ -320,7 +327,6 @@ var AbstractField = Widget.extend({
         this.$el.addClass('o_field_invalid');
         this.$el.attr('aria-invalid', 'true');
     },
-
     /**
      * Update the modifiers with the newest value.
      * Now this.attrs.modifiersValue can be used consistantly even with
diff --git a/addons/web/static/src/js/fields/basic_fields.js b/addons/web/static/src/js/fields/basic_fields.js
index b48ea9022f9..edea04e0e48 100644
--- a/addons/web/static/src/js/fields/basic_fields.js
+++ b/addons/web/static/src/js/fields/basic_fields.js
@@ -701,8 +701,8 @@ var FieldBoolean = AbstractField.extend({
         // The formatValue of boolean fields renders HTML elements similar to
         // the one rendered by the widget itself. Even though the event might
         // have been fired on the non-widget version of this field, we can still
-        // test the presence of its o_checkbox class.
-        if (activated && options && options.event && $(options.event.target).parents('.o_checkbox').length) {
+        // test the presence of its custom class.
+        if (activated && options && options.event && $(options.event.target).closest('.custom-control.custom-checkbox').length) {
             this._setValue(!this.value);  // Toggle the checkbox
         }
         return activated;
@@ -737,6 +737,15 @@ var FieldBoolean = AbstractField.extend({
         }
         return rendered;
     },
+    /**
+     * Associates the 'for' attribute of the internal label.
+     *
+     * @override
+     */
+    setIDForLabel: function (id) {
+        this._super.apply(this, arguments);
+        this.$('.custom-control-label').attr('for', id);
+    },
 
     //--------------------------------------------------------------------------
     // Private
diff --git a/addons/web/static/src/js/fields/relational_fields.js b/addons/web/static/src/js/fields/relational_fields.js
index 73bcc1f1f35..ba83de415e7 100644
--- a/addons/web/static/src/js/fields/relational_fields.js
+++ b/addons/web/static/src/js/fields/relational_fields.js
@@ -1887,7 +1887,7 @@ var FormFieldMany2ManyTags = FieldMany2ManyTags.extend({
             this.$color_picker.dropdown('toggle');
             this.$color_picker.attr("tabindex", 1).focus();
             if (!tagColor) {
-                this.$('.o_checkbox input').prop('checked', true);
+                this.$('.custom-checkbox input').prop('checked', true);
             }
         }
     },
@@ -1909,7 +1909,7 @@ var FormFieldMany2ManyTags = FieldMany2ManyTags.extend({
         var changes = {};
 
         if ($target.is('.o_hide_in_kanban')) {
-            var $checkbox = $('.o_hide_in_kanban .o_checkbox input');
+            var $checkbox = $('.o_hide_in_kanban .custom-checkbox input');
             $checkbox.prop('checked', !$checkbox.prop('checked')); // toggle checkbox
             this.prevColors = this.prevColors ? this.prevColors : {};
             if ($checkbox.is(':checked')) {