feat: implement data reception layer with WebSocket and HTTP support

[Jopsan-gm]

🚀 Neko Pull Request

Mark with an x all the checkboxes that apply (like [x])

• Closes Data Reception Layer #16
• Added tests (if necessary)
• Run tests
• Run formatting
• Evidence attached (Add your Loom/Cap video link here)
• Commented the code

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📌 Type of Change

• Documentation (updates to README, docs, or comments)
• Bug fix (non-breaking change which fixes an issue)
• Enhancement (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

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📝 Changes description

Implemented the Data Reception Layer for the Aggregator service, enabling efficient communication with the Ingestor service.

Key Features:

• WebSocket Client: Real-time connection to receive price streams.
• Automatic Reconnection: Implementation of retry logic using Exponential Backoff (maximum 5 attempts).
• HTTP Fallback: Methods to retrieve price snapshots and historical data via REST requests.
• Data Validation: Used class-validator and class-transformer to ensure the integrity of incoming messages (DTOs).
• Event-Driven Architecture: Emits internal events (price.received) using EventEmitter2 for asynchronous processing.
• Unit Testing: Achieved >80% coverage using mocks for WebSocket and HttpService.
• Documentation: Updated README.md and .env.example.

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📸 Evidence (A Loom/Cap video is required as evidence, we WON'T merge if there's no proof)

Test Execution Results:

• Test Suites: 1 passed, 1 total
• Tests: 14 passed, 14 total

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⏰ Time spent breakdown

• Research and Project Structure: 0.5h
• DataReceptionService Implementation (WS/HTTP): 1.5h
• Validation and DTOs: 0.5h
• Unit Testing and Coverage: 1.0h
• Documentation and Refactoring: 0.5h
• Total: ~4.0h

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🌌 Comments

The service is designed to be resilient to network failures thanks to the reconnection logic. NestJS best practices were followed, utilizing dependency injection and decorators throughout the implementation.

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Thank you for contributing to Neko, you just helped us make RWAs consumer friendly on Stellar! We hope you can continue contributing to this project.

[Jopsan-gm]

Hi @FabianSanchezD Could you please review my issue?

[FabianSanchezD]

LGTM