add update post endpoint

dbTools/post.js

@@ -19,6 +19,23 @@ postDB = (DB)=>{
         });
     }
 
+    DB.updatePost = (postid, newContent, oldContent) => {
+        const id = DB.ObjectID(postid);
+        let update = {
+            $set:{
+                content: newContent,
+                // lastUpdated: new Date() // add back when finish updating videos.
+            },
+            $push: {
+                contentHistory: oldContent
+            }
+        }
+        return DB.postCols.updateOne({_id: id}, update).catch((err)=>{
+            console.log(err);
+            return false;
+        });
+    }
+
     DB.newReaction = (postid, profileid, reaction) => {
         const id = DB.ObjectID(postid);
         let update = {