[FIX] mail: fully show message action list in chat window

Before this commit, squashed messages in chat window had part of
the action list being cut by the message above.

This comes from `overflow-auto` on the message content, which was
defined to make content shrink, but had the unintended side-effect
of cutting the message action list for squashed messages in chat
window.

This commit fixes the solution by using `min-width: 0;` instead to
shrink flex item to lower of content width. This style-rule works
like setting `overflow-auto` without actually affecting overflow.

X-original-commit: 3e4b32361ade567d8d4fde37f0ed2542a3e2e215
Part-of: odoo/odoo#123526

addons/mail/static/src/core_ui/core.scss

@@ -0,0 +1,7 @@
+.o-bg-inherit {
+    background-color: inherit;
+}
+
+.o-min-width-0 {
+    min-width: 0;
+}

addons/mail/static/src/core_ui/message.xml

@@ -33,7 +33,7 @@
                             </div>
                         </t>
                     </div>
-                    <div class="w-100 overflow-auto" t-att-class="{ 'flex-grow-1': message.composer }" t-ref="messageContent">
+                    <div class="w-100 o-min-width-0" t-att-class="{ 'flex-grow-1': message.composer }" t-ref="messageContent">
                         <div t-if="!props.squashed" class="o-mail-Message-header d-flex flex-wrap align-items-baseline mb-1 lh-1">
                             <span t-if="(message.author or message.email_from) and shouldDisplayAuthorName" class="o-mail-Message-author" t-att-class="{ 'cursor-pointer o_redirect': hasAuthorClickable }" t-att-title="authorText" t-on-click="ev => this.onClickAuthor(ev)">
                                 <strong class="me-1 text-truncate"><t t-if="message.author" t-esc="message.author.name"/><t t-else="" t-esc="message.email_from"/></strong>

addons/mail/static/src/discuss_app/im_status.scss

@@ -7,7 +7,3 @@
         color: $yellow;
     }
 }
-
-.o-bg-inherit {
-    background-color: inherit;
-}

addons/mail/static/src/web/chatter.scss

@@ -28,13 +28,9 @@
     height: $o-mail-Avatar-sizeSmall;
 }
 
-.o-mail-Follower-details {
-    min-width: 0;
-
-    &:hover {
-        background: $gray-400;
-        color: $black;
-    }
+.o-mail-Follower-details:hover {
+    background: $gray-400;
+    color: $black;
 }
 
 .o-mail-Follower-action:hover {

addons/mail/static/src/web/chatter.xml

@@ -36,7 +36,7 @@
                         </t>
                         <t t-if="state.thread.followers.length > 0">
                             <div t-foreach="state.thread.followers" t-as="follower" t-key="follower.id" class="dropdown-item o-mail-Follower d-flex justify-content-between p-0">
-                                <a class="o-mail-Follower-details d-flex align-items-center flex-grow-1 px-3 text-700" t-att-class="{ 'o-inactive fst-italic opacity-25': !follower.isActive }" href="#" role="menuitem" t-on-click.prevent="(ev) => this.onClickDetails(ev, follower)">
+                                <a class="o-mail-Follower-details d-flex align-items-center flex-grow-1 px-3 text-700 o-min-width-0" t-att-class="{ 'o-inactive fst-italic opacity-25': !follower.isActive }" href="#" role="menuitem" t-on-click.prevent="(ev) => this.onClickDetails(ev, follower)">
                                     <img class="o-mail-Follower-avatar me-2 rounded" t-att-src="threadService.avatarUrl(follower.partner, state.thread)" alt=""/>
                                     <span class="flex-shrink text-truncate" t-esc="follower.partner.name"/>
                                 </a>