Delete tag API (#13358)

* Delete tag API

Signed-off-by: jolheiser <john.olheiser@gmail.com>

* Wording

Signed-off-by: jolheiser <john.olheiser@gmail.com>

* Add conflict response and fix API tests

Signed-off-by: jolheiser <john.olheiser@gmail.com>

* Fix other test

Signed-off-by: jolheiser <john.olheiser@gmail.com>

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

models/fixtures/release.yml

@@ -27,3 +27,19 @@
   is_prerelease: false
   is_tag: false
   created_unix: 946684800
+
+-
+  id: 3
+  repo_id: 1
+  publisher_id: 2
+  tag_name: "delete-tag"
+  lower_tag_name: "delete-tag"
+  target: "master"
+  title: "delete-tag"
+  sha1: "65f1bf27bc3bf70f64657658635e66094edbcb4d"
+  num_commits: 10
+  is_draft: false
+  is_prerelease: false
+  is_tag: true
+  created_unix: 946684800
+