Add api for list agents and agent seesions (#3835)

### What problem does this PR solve?

Add api for list agents and agent seesions

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

Co-authored-by: liuhua <10215101452@stu.ecun.edu.cn>

api/db/services/canvas_service.py

@@ -25,3 +25,22 @@ class CanvasTemplateService(CommonService):
 
 class UserCanvasService(CommonService):
     model = UserCanvas
+
+    @classmethod
+    @DB.connection_context()
+    def get_list(cls, tenant_id,
+                 page_number, items_per_page, orderby, desc, id, title):
+        agents = cls.model.select()
+        if id:
+            agents = agents.where(cls.model.id == id)
+        if title:
+            agents = agents.where(cls.model.title == title)
+        agents = agents.where(cls.model.user_id == tenant_id)
+        if desc:
+            agents = agents.order_by(cls.model.getter_by(orderby).desc())
+        else:
+            agents = agents.order_by(cls.model.getter_by(orderby).asc())
+
+        agents = agents.paginate(page_number, items_per_page)
+
+        return list(agents.dicts())