Little tweaks to make it work... In a devcontainer anyway....

backend/src/models/message.js

@@ -0,0 +1,55 @@
+const Images = require('../modules/images');
+const Logger = require('../modules/logger');
+const Mongoose = require('mongoose');  
+
+const MessageSchema = new Mongoose.Schema({
+  "text" : { type: String },
+  "image" : { type: String, index: true },
+  "isUser" : { type: Boolean, default: false, required: true, index: true },
+  "timestamp": { type: Date, default: Date.now() }
+});
+
+MessageSchema.pre('findOneAndUpdate', function (next) {
+  var message = this;
+  
+  if (message.image && typeof message.image === 'object') {
+    Images.saveMessageImage(message.image, (err, filename) => {
+      if (err) {
+        Logger.error('[MessageSchema.pre(save)] There was an error processing the message image. [' + err + ']', { error: err });
+      }
+      
+      if (filename) {
+        message.image = filename;
+        next();
+      }
+    })
+  } else {
+    next();
+  }
+});
+
+MessageSchema.pre('save', function (next) {
+  var message = this;
+  
+  if (message.image && typeof message.image === 'object') {
+    Images.saveMessageImage(message.image, (err, filename) => {
+      if (err) {
+        Logger.error('[MessageSchema.pre(save)] There was an error processing the message image. [' + err + ']', { error: err });
+      }
+      
+      if (filename) {
+        message.image = filename;
+        next();
+      }
+    })
+  } else {
+    next();
+  }
+});
+
+const MessageModel = Mongoose.model('messages', MessageSchema);
+
+module.exports = {
+  schema: MessageSchema,
+  model: MessageModel
+};