feat(node-gateway):Add openapi spec

Signed-off-by: Jitpanu Maneeratpongsuk <jitpanu.maneeratpongsuk@rwth-aachen.de>

Author: JitpanuM

doc/openapi/components/schemas/config/nodes/_gateway.yaml

@@ -0,0 +1,7 @@
+# yaml-language-server: $schema=http://json-schema.org/draft-07/schema
+# SPDX-FileCopyrightText: 2014-2023 Institute for Automation of Complex Power Systems, RWTH Aachen University
+# SPDX-License-Identifier: Apache-2.0
+---
+allOf:
+- $ref: ../node_obj.yaml
+- $ref: gateway.yaml

doc/openapi/components/schemas/config/nodes/gateway.yaml

@@ -0,0 +1,15 @@
+# yaml-language-server: $schema=http://json-schema.org/draft-07/schema
+# SPDX-FileCopyrightText: 2014-2023 Institute for Automation of Complex Power Systems, RWTH Aachen University
+# SPDX-License-Identifier: Apache-2.0
+---
+allOf:
+- type: object
+  properties:
+    format:
+      $ref: ../format_spec.yaml
+    gateway_type:
+      type: string
+    address:
+      type: string
+
+- $ref: ../node.yaml