Added the ability to save sketches

Implemented by exposing an RPC method to save the sketch and calling
from JS using `frappe.call`. Any logged-in user can create new sketches
and the owner can edit his/her own sketches.

community/www/sketches/sketch.py

@@ -5,6 +5,15 @@ def get_context(context):
     course_name = get_queryparam("sketch", '/sketches')
     context.sketch = get_sketch(course_name)
     context.livecode_url = get_livecode_url()
+    context.editable = is_editable(context.sketch, frappe.sesson.user)
+
+def is_editable(sketch, user):
+    if sketch.name == "new":
+        # new sketches can be editable by any logged in user
+        return user != "Guest"
+    else:
+        # existing sketches are editable by the owner
+        return sketch.owner == user
 
 def get_livecode_url():
     doc = frappe.get_doc("LMS Settings")
@@ -20,15 +29,13 @@ def get_queryparam(name, redirect_when_not_found):
 def get_sketch(name):
     if name == 'new':
         sketch = frappe.new_doc('LMS Sketch')
+        sketch.name = "new"
         sketch.title = "New Sketch"
         sketch.code = "circle(100, 100, 50)"
-        sketch.owner = frappe.session.user.split("@")[0]
         return sketch
 
     try:
-        sketch = frappe.get_doc('LMS Sketch', name)
+        return frappe.get_doc('LMS Sketch', name)
     except frappe.exceptions.DoesNotExistError:
         raise frappe.NotFound
 
-    sketch.owner = sketch.owner.split("@")[0]
-    return sketch