Refactor id generator to it's own package

id/generator.go

@@ -0,0 +1,5 @@
+package id
+
+type Generator interface {
+	NewId() string
+}

id/mock.go

@@ -0,0 +1,12 @@
+package id
+
+import "github.com/stretchr/testify/mock"
+
+type MockGenerator struct {
+	mock.Mock
+}
+
+func (m *MockGenerator) NewId() string {
+	args := m.Called()
+	return args.String(0)
+}

id/xid.go

@@ -0,0 +1,10 @@
+package id
+
+import "github.com/rs/xid"
+
+type XIDGenerator struct {
+}
+
+func (x XIDGenerator) NewId() string {
+	return xid.New().String()
+}