[Mass Mailing] Plain text template, disable the snippets

Make plain text mode more user-friendly and behave like gmail

* No snippet bar for plain text template
* once the plain text template selected, the cursor should be in the mail or
add a placeholder
* Default Unsubscribe link in the plain text template
* Don't force the font type; Let each email client use its own default font.

opw-1852811

addons/mass_mailing/static/src/css/basic_theme_readonly.css

@@ -0,0 +1,7 @@
+/* We want to show system's default font in the mail sent with the basic theme.
+   And so we remove font-family from basic theme while saving. But by doing so
+   in readonly mode is not getting proper font in odoo. So we added if from here.
+ */
+#wrapwrap .o_layout.o_basic_theme {
+    font-family: -apple-system, "HelveticaNeue", "Helvetica Neue", Helvetica, Arial, "Lucida Grande", sans-serif;
+}

addons/mass_mailing/static/src/js/mass_mailing_editor.js

@@ -362,10 +362,21 @@ snippets_editor.Class.include({
 
             if (first_choice) {
                 self._registerDefaultTexts($new_wrapper_content);
+                if(theme_params.name == 'basic') {
+                    $editable_area.focusIn();
+                }
             }
             self._disableUndroppableSnippets();
         }
     },
+    cleanForSave: function () {
+        this._super.apply(this, arguments);
+        // remove font-family from all elements for plain text theme (just like gmail)
+        var $basicTheme = this.$editable.find('.o_basic_theme');
+        if($basicTheme.length && this.$editable.data('oe-model') === 'mail.mass_mailing') {
+            this.$editable.find('*').css('font-family', '');
+        }
+    }
 });
 
 var callback = window ? window["callback"] : undefined;

addons/mass_mailing/static/src/scss/mass_mailing.ui.scss

@@ -41,6 +41,9 @@
 
         .dropdown-item { 
             padding: 10px 10px;
+            &:first-child {
+                display: none;
+            }
 
             .o_thumb {
                 display: none;
@@ -91,6 +94,10 @@ body.o_force_mail_theme_choice {
                     max-width: 25%;
                     transition: all 0.3s ease 0s;
 
+                    &:first-child {
+                        display: block;
+                    }
+
                     .o_thumb {
                         display: none;
                         padding-top: 107%;
@@ -153,6 +160,12 @@ body.o_force_mail_theme_choice {
 }
 
 #web_editor_inside_iframe {
+    &.o_basic_theme {
+        padding-left: 0px !important;
+        #oe_snippets {
+            display: none;
+        }
+    }
     #wrapwrap > main #editable_area {
         padding: 24px;
     }

addons/mass_mailing/views/editor_field_html.xml

@@ -13,6 +13,9 @@
                 <t t-call-assets="mass_mailing.assets_mail_themes"/>
                 <script type="text/javascript" src="/mass_mailing/static/src/js/mass_mailing_editor.js"></script>
             </t>
+            <t t-else="">
+                <link rel="stylesheet" href="/mass_mailing/static/src/css/basic_theme_readonly.css" type="text/css"/>
+            </t>
             <base target="_parent"/>
         </t>
         <t t-set="head" t-value="head_mm_field_text_html_inline + (head or '')"/>

addons/mass_mailing/views/themes_templates.xml

@@ -3,8 +3,11 @@
     <!-- Theme "Basic" template -->
     <template id="theme_basic_template">
         <div class="o_mail_no_options">
+            <p><br/></p>
+            <p><br/></p>
             <p>
                 <br/>
+                <a href="/unsubscribe_from_list">Unsubscribe</a>
             </p>
         </div>
     </template>