💻 Add adventure within customize class (#5313)

Fixes #4084 

**How to test:**
1. Go to `/customize-class`
2. Next to the Reset button (top right), click 'Create adventure'. 
3. Check that the Adventure is correctly added to the level and the class you were in.


https://github.com/hedyorg/hedy/assets/48122190/0a5cb4ee-d231-4328-99fa-d9a86e9b8072

templates/customize-class/partial-sortable-adventures.html

@@ -36,6 +36,17 @@ <h3 class="flex-1">{{_('select_adventures')}}</h3>
                     >
                     {{_('reset_button')}}
                 </button>
+                <div class="flex flex-row">
+                    <button id="create_adventure_button" class="green-btn" 
+                    hx-trigger="click"
+                    hx-post="/for-teachers/create-adventure/{{class_id}}/{{level}}"
+                    hx-swap="none"
+                    _="on htmx:afterRequest if detail.xhr.response
+                    window.open('/for-teachers/customize-adventure/' + detail.xhr.response, '_self')"
+                    data-cy="edit-link"{% if second_teacher and role == 'viewer' %}disabled{% endif %}>
+                    {{_('create_adventure')}}
+                    </button>
+                    </div>
             </div>
         </div>
         <div class="flex items-center min-w-max">

website/for_teachers.py

@@ -1187,8 +1187,9 @@ def add_adventure_to_class_level(self, user, class_id, adventure_id, level, remo
 
     @route("/create-adventure/", methods=["POST"])
     @route("/create-adventure/<class_id>", methods=["POST"])
+    @route("/create-adventure/<class_id>/<level>", methods=["POST"])
     @requires_teacher
-    def create_adventure(self, user, class_id=None):
+    def create_adventure(self, user, class_id=None, level=None):
         if not is_teacher(user) and not is_admin(user):
             return utils.error_page(error=403, ui_message=gettext("retrieve_class_error"))
 
@@ -1200,21 +1201,24 @@ def create_adventure(self, user, class_id=None):
                 name += 'X'
                 continue
 
+        if not level:
+            level = "1"
+
         session['class_id'] = class_id
         adventure = {
             "id": adventure_id,
             "date": utils.timems(),
             "creator": user["username"],
             "name": name,
             "classes": [class_id],
-            "level": 1,
-            "levels": ["1"],
+            "level": int(level),
+            "levels": [level],
             "content": "",
             "public": 0,
             "language": g.lang,
         }
         self.db.store_adventure(adventure)
         if class_id:
-            self.add_adventure_to_class_level(user, class_id, adventure_id, "1", False)
+            self.add_adventure_to_class_level(user, class_id, adventure_id, str(level), False)
 
         return adventure["id"], 200