chore: Strip unsupported signature formatting by channel (#13046)

# Pull Request Template

## Description

1. This PR is an enhancement to
https://github.com/chatwoot/chatwoot/pull/13045
It strips unsupported formatting from **message signatures** based on
each channel’s formatting capabilities defined in the `FORMATTING`
config

2. Remove usage of plain editor in Compose new conversation modal

Only the following signature elements are considered:
<strong>bold (<code inline="">strong</code>), italic (<code
inline="">em</code>), links (<code inline="">link</code>), images (<code
inline="">image</code>)</strong>.</p>

Any formatting not supported by the target channel is automatically
removed before the signature is appended.

<h3>Channel-wise Signature Formatting Support</h3>

Channel | Keeps in Signature | Strips from Signature
-- | -- | --
Email | bold, italic, links, images | —
WebWidget | bold, italic, links, images | —
API | bold, italic | links, images
WhatsApp | bold, italic | links, images
Telegram | bold, italic, links | images
Facebook | bold, italic | links, images
Instagram | bold, italic | links, images
Line | bold, italic | links, images
SMS | — | everything
Twilio SMS | — | everything
Twitter/X | — | everything


<hr>
<h3>📝 Note</h3>
<blockquote>
<p>Message signatures only support <strong>bold, italic, links, and
images</strong>.<br>
Other formatting options available in the editor (lists, code blocks,
strike-through, etc.) do <strong>not apply</strong> to signatures and
are ignored.</p>
</blockquote>

## Type of change

- [x] New feature (non-breaking change which adds functionality)

## How Has This Been Tested?

### Loom video
https://www.loom.com/share/d325ab86ca514c6d8f90dfe72a8928dd


## Checklist:

- [x] My code follows the style guidelines of this project
- [x] I have performed a self-review of my code
- [x] 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
- [x] 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

---------

Co-authored-by: Muhsin Keloth <muhsinkeramam@gmail.com>

app/javascript/dashboard/components/widgets/WootWriter/Editor.vue

@@ -54,6 +54,7 @@ import {
   getFormattingForEditor,
   getSelectionCoords,
   calculateMenuPosition,
+  getEffectiveChannelType,
 } from 'dashboard/helper/editorHelper';
 import {
   hasPressedEnterAndNotCmdOrShift,
@@ -81,6 +82,7 @@ const props = defineProps({
   // are triggered except when this flag is true
   allowSignature: { type: Boolean, default: false },
   channelType: { type: String, default: '' },
+  medium: { type: String, default: '' },
   showImageResizeToolbar: { type: Boolean, default: false }, // A kill switch to show or hide the image toolbar
   focusOnMount: { type: Boolean, default: true },
 });
@@ -105,10 +107,16 @@ const TYPING_INDICATOR_IDLE_TIME = 4000;
 const MAXIMUM_FILE_UPLOAD_SIZE = 4; // in MB
 const DEFAULT_FORMATTING = 'Context::Default';
 
+const effectiveChannelType = computed(() =>
+  getEffectiveChannelType(props.channelType, props.medium)
+);
+
 const editorSchema = computed(() => {
   if (!props.channelType) return messageSchema;
 
-  const formatType = props.isPrivate ? DEFAULT_FORMATTING : props.channelType;
+  const formatType = props.isPrivate
+    ? DEFAULT_FORMATTING
+    : effectiveChannelType.value;
   const formatting = getFormattingForEditor(formatType);
   return buildMessageSchema(formatting.marks, formatting.nodes);
 });
@@ -116,7 +124,7 @@ const editorSchema = computed(() => {
 const editorMenuOptions = computed(() => {
   const formatType = props.isPrivate
     ? DEFAULT_FORMATTING
-    : props.channelType || DEFAULT_FORMATTING;
+    : effectiveChannelType.value || DEFAULT_FORMATTING;
   const formatting = getFormattingForEditor(formatType);
   return formatting.menu;
 });
@@ -301,8 +309,13 @@ function isBodyEmpty(content) {
 
   // if the signature is present, we need to remove it before checking
   // note that we don't update the editorView, so this is safe
+  // Use effective channel type to match how signature was appended
   const bodyWithoutSignature = props.signature
-    ? removeSignatureHelper(content, props.signature)
+    ? removeSignatureHelper(
+        content,
+        props.signature,
+        effectiveChannelType.value
+      )
     : content;
 
   // trimming should remove all the whitespaces, so we can check the length
@@ -370,7 +383,11 @@ function addSignature() {
   // see if the content is empty, if it is before appending the signature
   // we need to add a paragraph node and move the cursor at the start of the editor
   const contentWasEmpty = isBodyEmpty(content);
-  content = appendSignature(content, props.signature, props.channelType);
+  content = appendSignature(
+    content,
+    props.signature,
+    effectiveChannelType.value
+  );
   // need to reload first, ensuring that the editorView is updated
   reloadState(content);
 
@@ -382,7 +399,11 @@ function addSignature() {
 function removeSignature() {
   if (!props.signature) return;
   let content = props.modelValue;
-  content = removeSignatureHelper(content, props.signature);
+  content = removeSignatureHelper(
+    content,
+    props.signature,
+    effectiveChannelType.value
+  );
   // reload the state, ensuring that the editorView is updated
   reloadState(content);
 }

app/javascript/dashboard/components/widgets/conversation/ReplyBox.vue

@@ -43,6 +43,7 @@ import fileUploadMixin from 'dashboard/mixins/fileUploadMixin';
 import {
   appendSignature,
   removeSignature,
+  getEffectiveChannelType,
 } from 'dashboard/helper/editorHelper';
 
 import { LOCAL_STORAGE_KEYS } from 'dashboard/constants/localStorage';
@@ -564,9 +565,13 @@ export default {
         return message;
       }
 
+      const effectiveChannelType = getEffectiveChannelType(
+        this.channelType,
+        this.inbox?.medium || ''
+      );
       return this.sendWithSignature
-        ? appendSignature(message, this.messageSignature, this.channelType)
-        : removeSignature(message, this.messageSignature);
+        ? appendSignature(message, this.messageSignature, effectiveChannelType)
+        : removeSignature(message, this.messageSignature, effectiveChannelType);
     },
     removeFromDraft() {
       if (this.conversationIdByRoute) {
@@ -757,10 +762,14 @@ export default {
         // if signature is enabled, append it to the message
         // appendSignature ensures that the signature is not duplicated
         // so we don't need to check if the signature is already present
+        const effectiveChannelType = getEffectiveChannelType(
+          this.channelType,
+          this.inbox?.medium || ''
+        );
         message = appendSignature(
           message,
           this.messageSignature,
-          this.channelType
+          effectiveChannelType
         );
       }
 
@@ -800,10 +809,14 @@ export default {
       this.message = '';
       if (this.sendWithSignature && !this.isPrivate) {
         // if signature is enabled, append it to the message
+        const effectiveChannelType = getEffectiveChannelType(
+          this.channelType,
+          this.inbox?.medium || ''
+        );
         this.message = appendSignature(
           this.message,
           this.messageSignature,
-          this.channelType
+          effectiveChannelType
         );
       }
       this.attachedFiles = [];
@@ -1121,6 +1134,7 @@ export default {
         :signature="messageSignature"
         allow-signature
         :channel-type="channelType"
+        :medium="inbox.medium"
         @typing-off="onTypingOff"
         @typing-on="onTypingOn"
         @focus="onFocus"