#close 129 feat: add validatePocketPayConfig helper for early SDK configuration validation

[emmyoat]

Summary

Adds a non-throwing configuration validation helper (validatePocketPayConfig) to allow consumers to validate SDK configuration settings early before initiating network or transaction operations.

Solution

Implemented validatePocketPayConfig which evaluates configuration options and returns a structured ConfigValidationResult containing:

• valid: boolean (true when zero errors exist)
• errors: Array of fatal configuration issues
• warnings: Array of non-fatal advisory issues (e.g., insecure HTTP URLs, network/endpoint mismatches, extreme timeouts)
• issues: Complete list of all errors and warnings
• config: Resolved SDKConfig (populated when valid is true)

Key Changes

• Types (src/types/index.ts): Added ConfigIssueSeverity, ConfigValidationIssue, and ConfigValidationResult.
• Config Helper (src/config/index.ts): Added validatePocketPayConfig() and integrated sanitizeValue/redactSensitive so sensitive patterns (e.g., Stellar secret keys S...) are sanitized in validation output (S[REDACTED]).
• Package Exports (src/index.ts): Re-exported validatePocketPayConfig and configuration validation result types from the package root.
• Unit Tests (tests/config-validation.test.ts): Added tests covering default testnet configuration, explicit valid overrides, malformed/invalid parameters, advisory warnings, and secret key redaction.
• Documentation (docs/configuration.md): Added an "Early Configuration Validation" guide with structured return types and TypeScript usage examples.

Usage Example

import { validatePocketPayConfig } from 'stellar-pocketpay-sdk';

const result = validatePocketPayConfig({
  network: 'testnet',
  horizonUrl: 'https://horizon-testnet.stellar.org',
  timeout: 30000,
});

if (!result.valid) {
  console.error('Configuration errors:', result.errors);
} else {
  console.log('Resolved SDK Config:', result.config);
  if (result.warnings.length > 0) {
    console.warn('Configuration warnings:', result.warnings);
  }
}

[El-swaggerito]

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