add a system tag push example

testdata/gitlab/system-tag-event.json

@@ -0,0 +1,38 @@
+{
+  "event_name": "tag_push",
+  "before": "0000000000000000000000000000000000000000",
+  "after": "82b3d5ae55f7080f1e6022629cdb57bfae7cccc7",
+  "ref": "refs/tags/v1.0.0",
+  "checkout_sha": "5937ac0a7beb003549fc5fd26fc247adbce4a52e",
+  "user_id": 1,
+  "user_name": "John Smith",
+  "user_avatar": "https://s.gravatar.com/avatar/d4c74594d841139328695756648b6bd6?s=8://s.gravatar.com/avatar/d4c74594d841139328695756648b6bd6?s=80",
+  "project_id": 1,
+  "project":{
+    "name":"Example",
+    "description":"",
+    "web_url":"http://example.com/jsmith/example",
+    "avatar_url":null,
+    "git_ssh_url":"[email protected]:jsmith/example.git",
+    "git_http_url":"http://example.com/jsmith/example.git",
+    "namespace":"Jsmith",
+    "visibility_level":0,
+    "path_with_namespace":"jsmith/example",
+    "default_branch":"master",
+    "homepage":"http://example.com/jsmith/example",
+    "url":"[email protected]:jsmith/example.git",
+    "ssh_url":"[email protected]:jsmith/example.git",
+    "http_url":"http://example.com/jsmith/example.git"
+  },
+  "repository":{
+    "name": "Example",
+    "url": "ssh://[email protected]/jsmith/example.git",
+    "description": "",
+    "homepage": "http://example.com/jsmith/example",
+    "git_http_url":"http://example.com/jsmith/example.git",
+    "git_ssh_url":"[email protected]:jsmith/example.git",
+    "visibility_level":0
+  },
+  "commits": [],
+  "total_commits_count": 0
+}