feat(center-nodes): enforce nodeId and endpoint uniqueness

Fabric.Backend.Center/src/nodes/nodes.controller.ts

@@ -1,5 +1,6 @@
 import {
   Body,
+  ConflictException,
   Controller,
   ForbiddenException,
   Get,
@@ -23,6 +24,20 @@ export class NodesController {
       throw new ForbiddenException('invalid shared secret');
     }
 
+    const existedByNodeId = await this.nodeRepo.findOne({
+      where: { nodeId: body.nodeId },
+    });
+    if (existedByNodeId) {
+      throw new ConflictException('nodeId already exists');
+    }
+
+    const existedByEndpoint = await this.nodeRepo.findOne({
+      where: { endpoint: body.endpoint },
+    });
+    if (existedByEndpoint) {
+      throw new ConflictException('endpoint already exists');
+    }
+
     const node = this.nodeRepo.create({
       nodeId: body.nodeId,
       name: body.name,