Add dynamic pricing E2E test suite with Playwright

Implement comprehensive E2E tests to validate the surge pricing pipeline:
- Test SimpleSurgePricer with configurable thresholds (high=3, surge=1.5x)
- Verify discount pricing when demand is below low_threshold
- Test multi-product differential pricing based on demand signals
- Validate price propagation from pipeline through Redis to API

Test infrastructure:
- Playwright configuration with custom fixtures
- Python pipeline worker for direct test execution (bypasses Airflow)
- API client for event ingestion and price verification
- Event generator for creating realistic interaction sequences
- docker-compose.e2e.yml with minimal services for testing

e2e/lib/api-client.ts

@@ -0,0 +1,191 @@
+import { testConfig } from '../playwright.config';
+
+/**
+ * Event payload structure matching the backend API
+ */
+export interface EventPayload {
+  sessionId: string;
+  experimentId?: string;
+  eventName: string;
+  page: string;
+  productId?: string;
+  metadata?: Record<string, unknown>;
+  storeMode: 'hotel' | 'airline';
+  userAgent?: string;
+  ts?: string;
+}
+
+/**
+ * Price log payload structure
+ */
+export interface PriceLogPayload {
+  productId: string;
+  price: number;
+  sessionId: string;
+  experimentId?: string;
+  storeMode: 'hotel' | 'airline';
+  ts?: string;
+}
+
+/**
+ * Price response from the pricing provider
+ */
+export interface PriceResponse {
+  productId: string;
+  price: number;
+  base_price: number;
+  markup: number;
+  elasticity: number | null;
+  model_version: string;
+}
+
+/**
+ * API client for interacting with PHANTOM services
+ */
+export class PhantomApiClient {
+  private backendUrl: string;
+  private providerUrl: string;
+
+  constructor(
+    backendUrl: string = testConfig.backendUrl,
+    providerUrl: string = testConfig.providerUrl
+  ) {
+    this.backendUrl = backendUrl;
+    this.providerUrl = providerUrl;
+  }
+
+  /**
+   * Send a user interaction event to the ingestion API
+   */
+  async ingestEvent(event: EventPayload): Promise<{ success: boolean }> {
+    const payload: EventPayload = {
+      ...event,
+      ts: event.ts || new Date().toISOString(),
+    };
+
+    const response = await fetch(`${this.backendUrl}/api/kafka/ingest`, {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify(payload),
+    });
+
+    if (!response.ok) {
+      throw new Error(`Failed to ingest event: ${response.status} ${await response.text()}`);
+    }
+
+    return response.json();
+  }
+
+  /**
+   * Send multiple events in rapid succession
+   */
+  async ingestEvents(events: EventPayload[], delayMs: number = 100): Promise<void> {
+    for (const event of events) {
+      await this.ingestEvent(event);
+      if (delayMs > 0) {
+        await new Promise(resolve => setTimeout(resolve, delayMs));
+      }
+    }
+  }
+
+  /**
+   * Log a price observation
+   */
+  async logPrice(priceLog: PriceLogPayload): Promise<{ success: boolean }> {
+    const payload: PriceLogPayload = {
+      ...priceLog,
+      ts: priceLog.ts || new Date().toISOString(),
+    };
+
+    const response = await fetch(`${this.backendUrl}/api/kafka/price-log`, {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify(payload),
+    });
+
+    if (!response.ok) {
+      throw new Error(`Failed to log price: ${response.status} ${await response.text()}`);
+    }
+
+    return response.json();
+  }
+
+  /**
+   * Get the current price for a product from the pricing provider
+   */
+  async getPrice(
+    mode: 'hotel' | 'airline',
+    productId: string,
+    sessionId?: string
+  ): Promise<PriceResponse> {
+    const params = new URLSearchParams();
+    if (sessionId) {
+      params.set('sessionId', sessionId);
+    }
+
+    const url = `${this.providerUrl}/api/${mode}/price/${productId}${params.toString() ? '?' + params.toString() : ''}`;
+    const response = await fetch(url);
+
+    if (!response.ok) {
+      throw new Error(`Failed to get price: ${response.status} ${await response.text()}`);
+    }
+
+    return response.json();
+  }
+
+  /**
+   * Dump events from Kafka topic for debugging
+   */
+  async dumpKafkaEvents(
+    topic: 'user-interactions' | 'price-logs' = 'user-interactions',
+    lastN?: number
+  ): Promise<{ success: boolean; count: number; data: unknown[] }> {
+    const params = new URLSearchParams({ topic });
+    if (lastN) {
+      params.set('last_n', String(lastN));
+    }
+
+    const response = await fetch(`${this.backendUrl}/api/kafka/dump?${params.toString()}`);
+
+    if (!response.ok) {
+      throw new Error(`Failed to dump Kafka events: ${response.status}`);
+    }
+
+    return response.json();
+  }
+
+  /**
+   * Check health of backend service
+   */
+  async checkBackendHealth(): Promise<{ status: string; kafka: string }> {
+    const response = await fetch(`${this.backendUrl}/health`);
+    return response.json();
+  }
+
+  /**
+   * Check health of pricing provider
+   */
+  async checkProviderHealth(): Promise<{ status: string; redis: boolean }> {
+    const response = await fetch(`${this.providerUrl}/health`);
+    return response.json();
+  }
+
+  /**
+   * List registered models in the pricing provider
+   */
+  async listModels(): Promise<Record<string, unknown>> {
+    const response = await fetch(`${this.providerUrl}/models`);
+    return response.json();
+  }
+
+  /**
+   * Reload models in the pricing provider
+   */
+  async reloadModels(): Promise<{ elasticity_loaded: boolean; pricing_model_loaded: boolean }> {
+    const response = await fetch(`${this.providerUrl}/models/reload`, { method: 'POST' });
+    return response.json();
+  }
+}
+
+// Singleton instance for convenience
+export const apiClient = new PhantomApiClient();