feat: Add plain-text editor for non-rich content channels (#13058)

# Pull Request Template

## Description

This PR restores the plain text editor for all channels except Website,
Email, and API.

## Type of change

- [x] Bug fix (non-breaking change which fixes an issue)


## Checklist:

- [x] My code follows the style guidelines of this project
- [x] I have performed a self-review of my code
- [ ] I have commented on my code, particularly in hard-to-understand
areas
- [ ] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [x] New and existing unit tests pass locally with my changes
- [ ] Any dependent changes have been merged and published in downstream
modules

app/javascript/dashboard/components-next/NewConversation/components/MessageEditor.vue

@@ -1,9 +1,10 @@
 <script setup>
+import { computed } from 'vue';
 import { useI18n } from 'vue-i18n';
 
 import Editor from 'dashboard/components-next/Editor/Editor.vue';
 
-defineProps({
+const props = defineProps({
   hasErrors: { type: Boolean, default: false },
   hasAttachments: { type: Boolean, default: false },
   sendWithSignature: { type: Boolean, default: false },
@@ -12,6 +13,8 @@ defineProps({
   medium: { type: String, default: '' },
 });
 
+const editorKey = computed(() => `editor-${props.channelType}-${props.medium}`);
+
 const { t } = useI18n();
 
 const modelValue = defineModel({
@@ -23,6 +26,7 @@ const modelValue = defineModel({
 <template>
   <div class="flex-1 h-full" :class="[!hasAttachments && 'min-h-[200px]']">
     <Editor
+      :key="editorKey"
       v-model="modelValue"
       :placeholder="
         t('COMPOSE_NEW_CONVERSATION.FORM.MESSAGE_EDITOR.PLACEHOLDER')