add limit to the rules api (#10152)

docs/querying/api.md

@@ -620,6 +620,7 @@ $ curl http://localhost:9090/api/v1/rules
                 ],
                 "file": "/rules.yaml",
                 "interval": 60,
+                "limit": 0,
                 "name": "example"
             }
         ]

web/api/v1/api.go

@@ -1164,6 +1164,7 @@ type RuleGroup struct {
 	// same array.
 	Rules          []Rule    `json:"rules"`
 	Interval       float64   `json:"interval"`
+	Limit          int       `json:"limit"`
 	EvaluationTime float64   `json:"evaluationTime"`
 	LastEvaluation time.Time `json:"lastEvaluation"`
 }
@@ -1216,6 +1217,7 @@ func (api *API) rules(r *http.Request) apiFuncResult {
 			Name:           grp.Name(),
 			File:           grp.File(),
 			Interval:       grp.Interval().Seconds(),
+			Limit:          grp.Limit(),
 			Rules:          []Rule{},
 			EvaluationTime: grp.GetEvaluationTime().Seconds(),
 			LastEvaluation: grp.GetLastEvaluation(),

web/api/v1/api_test.go

@@ -1470,6 +1470,7 @@ func testEndpoints(t *testing.T, api *API, tr *testTargetRetriever, es storage.E
 						Name:     "grp",
 						File:     "/path/to/file",
 						Interval: 1,
+						Limit:    0,
 						Rules: []Rule{
 							AlertingRule{
 								State:       "inactive",
@@ -1516,6 +1517,7 @@ func testEndpoints(t *testing.T, api *API, tr *testTargetRetriever, es storage.E
 						Name:     "grp",
 						File:     "/path/to/file",
 						Interval: 1,
+						Limit:    0,
 						Rules: []Rule{
 							AlertingRule{
 								State:       "inactive",
@@ -1555,6 +1557,7 @@ func testEndpoints(t *testing.T, api *API, tr *testTargetRetriever, es storage.E
 						Name:     "grp",
 						File:     "/path/to/file",
 						Interval: 1,
+						Limit:    0,
 						Rules: []Rule{
 							RecordingRule{
 								Name:   "recording-rule-1",