Adding a license cluster command

es.go

@@ -1802,3 +1802,24 @@ func (c *Client) RemoveIndexILMPolicy(index string) error {
 
 	return nil
 }
+
+// LicenseCluster takes in the Elasticsearch license encoded as a string
+func (c *Client) LicenseCluster(license string) error {
+	// If the license is empty, return an error
+	if license == "" {
+		return errors.New("license is required")
+	}
+
+	// Build the request to apply the license to the cluster
+	agent := c.buildPutRequest("_license").
+		Set("Content-Type", "application/json").
+		Send(license)
+
+	// Execute the request
+	_, err := handleErrWithBytes(agent)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}

es_test.go

@@ -2363,3 +2363,22 @@ func TestRemoveIndexILMPolicy(t *testing.T) {
 		t.Fatalf("Unexpected error. expected nil, got %s", err)
 	}
 }
+func TestLicenseCluster(t *testing.T) {
+	body := `{"license":{"start_date_in_millis":2728303200000,"uid":"asdfasdf-e"}}`
+
+	testSetup := &ServerSetup{
+		Method: "PUT",
+		Path:   "/_license",
+		Body:   body,
+	}
+
+	host, port, ts := setupTestServers(t, []*ServerSetup{testSetup})
+	defer ts.Close()
+	client := NewClient(host, port)
+
+	err := client.LicenseCluster(body)
+
+	if err != nil {
+		t.Errorf("Unexpected error expected nil, got %s", err)
+	}
+}