Resolves #13. Add a config param to completely disable Mojang textures provider

mojangtextures/nil_mojang_textures.go

@@ -0,0 +1,12 @@
+package mojangtextures
+
+import (
+	"github.com/elyby/chrly/api/mojang"
+)
+
+type NilProvider struct {
+}
+
+func (p *NilProvider) GetForUsername(username string) (*mojang.SignedTexturesResponse, error) {
+	return nil, nil
+}

mojangtextures/nil_mojang_textures_test.go

@@ -0,0 +1,14 @@
+package mojangtextures
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestNilProvider_GetForUsername(t *testing.T) {
+	provider := &NilProvider{}
+	result, err := provider.GetForUsername("username")
+	assert.Nil(t, result)
+	assert.Nil(t, err)
+}