🧪 [Testing] Add Unit Tests for `BaseAdapter` Abstract Class

Description:

🚀 Overview

We need to create a comprehensive test suite for our BaseAdapter abstract class in easyswitch/adapters/base.py to ensure all payment provider adapters inherit consistent behavior and meet interface requirements.

📋 Test Coverage Requirements

Core Abstract Methods

• send_payment() method contract validation
• check_status() method error handling
• refund() method partial/full refund scenarios
• validate_webhook() signature verification
• parse_webhook() payload normalization

Configuration & Initialization

• Adapter initialization with valid/invalid configs
• Credential validation (_validate_credentials())
• HTTP client initialization (get_client())
• Provider-specific settings loading

Utility Methods

• validate_transaction() with various currencies
• format_transaction() data transformation
• map_fields() provider field mapping
• get_normalize_status() status code conversion