add create problem api

problem/urls/admin.py

@@ -1,7 +1,8 @@
 from django.conf.urls import url
 
-from ..views.admin import TestCaseUploadAPI
+from ..views.admin import ProblemAPI, TestCaseUploadAPI
 
 urlpatterns = [
-    url(r"^test_case/upload$", TestCaseUploadAPI.as_view(), name="test_case_upload_api")
+    url(r"^test_case/upload$", TestCaseUploadAPI.as_view(), name="test_case_upload_api"),
+    url(r"^problem$", ProblemAPI.as_view(), name="problem_api")
 ]

problem/urls/oj.py

@@ -3,5 +3,5 @@ from django.conf.urls import url
 from ..views.oj import ProblemTagAPI
 
 urlpatterns = [
-    url(r"^tags$", ProblemTagAPI.as_view(), name="problem_tag_list_api")
+    url(r"^problem/tags$", ProblemTagAPI.as_view(), name="problem_tag_list_api")
 ]