feat(observability): add in-process metrics endpoint for qps latency and error-rate

Fabric.Backend.Center/src/app.module.ts

@@ -2,6 +2,8 @@ import { Module } from '@nestjs/common';
 import { TypeOrmModule } from '@nestjs/typeorm';
 import { buildTypeOrmConfig } from './database.config';
 import { HealthController } from './common/health.controller';
+import { MetricsController } from './common/metrics.controller';
+import { MetricsService } from './common/metrics.service';
 import { AuthModule } from './auth/auth.module';
 import { NodesModule } from './nodes/nodes.module';
 import { AuditModule } from './audit/audit.module';
@@ -13,6 +15,7 @@ import { AuditModule } from './audit/audit.module';
     AuthModule,
     NodesModule,
   ],
-  controllers: [HealthController],
+  controllers: [HealthController, MetricsController],
+  providers: [MetricsService],
 })
 export class AppModule {}