config: support multiple destination addresses (#1789)

* config: support multiple destination addresses

* use constructor for string slice

* add docs

* add test for multiple destinations

* fix name

config/custom_test.go

@@ -0,0 +1,39 @@
+package config
+
+import (
+	"encoding/json"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"gopkg.in/yaml.v2"
+)
+
+func TestStringSlice_UnmarshalJSON(t *testing.T) {
+	t.Run("string", func(t *testing.T) {
+		var slc StringSlice
+		json.Unmarshal([]byte(`"hello world"`), &slc)
+		assert.Equal(t, NewStringSlice("hello world"), slc)
+	})
+	t.Run("array", func(t *testing.T) {
+		var slc StringSlice
+		json.Unmarshal([]byte(`["a","b","c"]`), &slc)
+		assert.Equal(t, NewStringSlice("a", "b", "c"), slc)
+	})
+}
+
+func TestStringSlice_UnmarshalYAML(t *testing.T) {
+	t.Run("string", func(t *testing.T) {
+		var slc StringSlice
+		yaml.Unmarshal([]byte(`hello world`), &slc)
+		assert.Equal(t, NewStringSlice("hello world"), slc)
+	})
+	t.Run("array", func(t *testing.T) {
+		var slc StringSlice
+		yaml.Unmarshal([]byte(`
+- a
+- b
+- c
+`), &slc)
+		assert.Equal(t, NewStringSlice("a", "b", "c"), slc)
+	})
+}