chore: Replace multiple mixins to simgle use composables

app/javascript/dashboard/composables/useMessage.js

@@ -0,0 +1,22 @@
+import { computed } from 'vue';
+
+/**
+ * Composable for handling message-related computations.
+ * @param {Object} message - The message object to be processed.
+ * @returns {Object} An object containing computed properties for message content and attachments.
+ */
+export function useMessage(message) {
+  const messageContentAttributes = computed(() => {
+    const { content_attributes: attribute = {} } = message;
+    return attribute;
+  });
+
+  const hasAttachments = computed(() => {
+    return !!(message.attachments && message.attachments.length > 0);
+  });
+
+  return {
+    messageContentAttributes,
+    hasAttachments,
+  };
+}