add test case upload api

problem/urls/admin.py

@@ -0,0 +1,7 @@
+from django.conf.urls import url
+
+from ..views.admin import TestCaseUploadAPI
+
+urlpatterns = [
+    url(r"^test_case/upload$", TestCaseUploadAPI.as_view(), name="test_case_upload_api")
+]

problem/urls/oj.py

@@ -1,6 +1,6 @@
 from django.conf.urls import url
 
-from ..views import ProblemTagAPI
+from ..views.oj import ProblemTagAPI
 
 urlpatterns = [
     url(r"^tags$", ProblemTagAPI.as_view(), name="problem_tag_list_api")