Add regex support to template query

This allows us to use the regex feature to extract a substring
result from a variable template query.

Change-Id: If8a8fe4052f18cd37f4b90ba2eb9fc94e19b07ea

grafana_dashboards/schema/template/query.py

@@ -32,6 +32,7 @@ class Query(Base):
                        default=1): v.All(int, v.Range(min=0, max=2)),
             v.Optional('datasource'): v.All(str),
             v.Optional('hide'): v.All(int, v.Range(min=0, max=2)),
+            v.Optional('regex'): v.All(str),
         }
         query.update(self.base)
         return v.Schema(query)

tests/schema/fixtures/dashboard-0027.json

@@ -47,6 +47,15 @@
                         "refresh": 2,
                         "type": "query"
                     },
+                    {
+                        "includeAll": false,
+                        "multi": false,
+                        "name": "test_query_regex",
+                        "query": "*",
+                        "refresh": 2,
+                        "regex": "/.*?-foo-(.*)/",
+                        "type": "query"
+                    },
                     {
                         "current": {
                             "text": "undercloud",

tests/schema/fixtures/dashboard-0027.yaml

@@ -7,6 +7,11 @@ dashboard:
       type: query
       query: "*"
       refresh: 2
+    - name: test_query_regex
+      type: query
+      query: "*"
+      refresh: 2
+      regex: "/.*?-foo-(.*)/"
     - name: test_custom_1
       type: custom
       options: