VOL-1405 : First submission for read-only core

- Most of the logic was copied from the read-write implementation
- Added missing Get/List calls
- Added necessary targets in Makefile
- Added docker and k8s manifests

Amendments:

- Removed more unecessary code.
- Removed refs to kafka
- Adjustements to reflect comments
- Removed refs to kafka in manifests

Change-Id: Ife2ca13d3ae428923825f7c19d42359d60406839
diff --git a/ro_core/core/model_proxy.go b/ro_core/core/model_proxy.go
new file mode 100644
index 0000000..f5e6c3b
--- /dev/null
+++ b/ro_core/core/model_proxy.go
@@ -0,0 +1,62 @@
+/*
+ * Copyright 2019-present Open Networking Foundation
+
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+
+ * http://www.apache.org/licenses/LICENSE-2.0
+
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package core
+
+import (
+	"github.com/opencord/voltha-go/common/log"
+	"github.com/opencord/voltha-go/db/model"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
+	"strings"
+	"sync"
+)
+
+// ModelProxy controls requests made to the data model
+type ModelProxy struct {
+	rootProxy *model.Proxy
+	basePath  string
+	mutex     sync.RWMutex
+}
+
+func newModelProxy(basePath string, rootProxy *model.Proxy) *ModelProxy {
+	ga := &ModelProxy{}
+	ga.rootProxy = rootProxy
+
+	if strings.HasPrefix(basePath, "/") {
+		ga.basePath = basePath
+	} else {
+		ga.basePath = "/" + basePath
+	}
+
+	return ga
+}
+
+// Get retrieves information at the provided path
+func (mp *ModelProxy) Get(parts ...string) (interface{}, error) {
+	mp.mutex.Lock()
+	defer mp.mutex.Unlock()
+
+	rawPath := []string{mp.basePath}
+	rawPath = append(rawPath, parts...)
+	path := strings.Join(rawPath, "/")
+
+	log.Debugw("get-data", log.Fields{"path": path})
+
+	if data := mp.rootProxy.Get(path, 1, false, ""); data != nil {
+		return data, nil
+	}
+	return nil, status.Errorf(codes.NotFound, "data-path: %s", path)
+}