More app code migration (#5170)

* Migrate admin functions into app package

* More user function refactoring

* Move post functions into app package

app/brand.go

@@ -0,0 +1,49 @@
+// Copyright (c) 2017 Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+package app
+
+import (
+	"mime/multipart"
+	"net/http"
+
+	"github.com/mattermost/platform/einterfaces"
+	"github.com/mattermost/platform/model"
+	"github.com/mattermost/platform/utils"
+)
+
+func SaveBrandImage(imageData *multipart.FileHeader) *model.AppError {
+	brandInterface := einterfaces.GetBrandInterface()
+	if brandInterface == nil {
+		err := model.NewLocAppError("SaveBrandImage", "api.admin.upload_brand_image.not_available.app_error", nil, "")
+		err.StatusCode = http.StatusNotImplemented
+		return err
+	}
+
+	if err := brandInterface.SaveBrandImage(imageData); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func GetBrandImage() ([]byte, *model.AppError) {
+	if len(utils.Cfg.FileSettings.DriverName) == 0 {
+		err := model.NewLocAppError("GetBrandImage", "api.admin.get_brand_image.storage.app_error", nil, "")
+		err.StatusCode = http.StatusNotImplemented
+		return nil, err
+	}
+
+	brandInterface := einterfaces.GetBrandInterface()
+	if brandInterface == nil {
+		err := model.NewLocAppError("GetBrandImage", "api.admin.get_brand_image.not_available.app_error", nil, "")
+		err.StatusCode = http.StatusNotImplemented
+		return nil, err
+	}
+
+	if img, err := brandInterface.GetBrandImage(); err != nil {
+		return nil, err
+	} else {
+		return img, nil
+	}
+}