feat: add api liveness and readiness checks

backend/libs/infrastructure/src/index.ts

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+export * from './postgres/postgres.module';
+export * from './redis/redis.module';

backend/libs/infrastructure/src/postgres/postgres.module.ts

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+import { Inject, Injectable, Module, OnModuleDestroy } from '@nestjs/common';
+import { Pool } from 'pg';
+import { APP_ENVIRONMENT, AppEnvironment } from '../../../configuration/src';
+
+export const POSTGRES_POOL = Symbol('POSTGRES_POOL');
+
+export const postgresPoolProvider = {
+  provide: POSTGRES_POOL,
+  inject: [APP_ENVIRONMENT],
+  useFactory: (env: AppEnvironment) =>
+    new Pool({ connectionString: env.databaseUrl }),
+};
+
+@Injectable()
+class PostgresLifecycle implements OnModuleDestroy {
+  constructor(@Inject(POSTGRES_POOL) private readonly pool: Pool) {}
+
+  async onModuleDestroy(): Promise<void> {
+    await this.pool.end();
+  }
+}
+
+@Module({
+  providers: [postgresPoolProvider, PostgresLifecycle],
+  exports: [postgresPoolProvider],
+})
+export class PostgresModule {}

backend/libs/infrastructure/src/redis/redis.module.ts

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+import { Inject, Injectable, Module, OnModuleDestroy } from '@nestjs/common';
+import Redis from 'ioredis';
+import { APP_ENVIRONMENT, AppEnvironment } from '../../../configuration/src';
+
+export const REDIS_CLIENT = Symbol('REDIS_CLIENT');
+
+export const redisClientProvider = {
+  provide: REDIS_CLIENT,
+  inject: [APP_ENVIRONMENT],
+  useFactory: (env: AppEnvironment) =>
+    new Redis(env.redisUrl, { lazyConnect: false }),
+};
+
+@Injectable()
+class RedisLifecycle implements OnModuleDestroy {
+  constructor(@Inject(REDIS_CLIENT) private readonly client: Redis) {}
+
+  async onModuleDestroy(): Promise<void> {
+    await this.client.quit();
+  }
+}
+
+@Module({
+  providers: [redisClientProvider, RedisLifecycle],
+  exports: [redisClientProvider],
+})
+export class RedisModule {}