Bugfix: Add debug option to log response headers

[asein-sinch]

How to enable debug logs:

import winston from 'winston';
const winstonLogger = winston.createLogger({
  level: 'debug',
  transports: [new winston.transports.Console()],
  format: winston.format.logstash(),
});

new SinchClient({ projectId, keyId, keySecret, logger:  winstonLogger});

Debug logs:

[Sinch SDK][Debug][AvailableRegionsApi][ListAvailableRegions][401]
HTTP method: GET
URL: https://numbers.api.sinch.com/v1/projects/37b62a7b-0177-429a-bb0b-e10f848de0b8/availableRegions?types=LOCAL&types=MOBILE
Response Headers:  Headers {
  [Symbol(map)]: [Object: null prototype] {
    'www-authenticate': [
      'Bearer error="invalid_token", error_description="Jwt expired at 2023-10-02T14:57:08Z", error_uri="https://tools.ietf.org/html/rfc6750#section-3.1"'
    ],
    'cache-control': [ 'no-cache, no-store, max-age=0, must-revalidate' ],
    pragma: [ 'no-cache' ],
    expires: [ '0' ],
    'x-content-type-options': [ 'nosniff' ],
    'strict-transport-security': [ 'max-age=31536000 ; includeSubDomains' ],
    'x-frame-options': [ 'DENY' ],
    'x-xss-protection': [ '0' ],
    'referrer-policy': [ 'no-referrer' ],
    'x-envoy-upstream-service-time': [ '2' ],
    date: [ 'Tue, 02 Dec 2025 22:25:38 GMT' ],
    server: [ 'istio-envoy' ],
    connection: [ 'close' ],
    'content-length': [ '0' ]
  }
}

[JPPortier]

We should think about supporting also for this SDK a logger interface.

[asein-sinch]

Added logger

[JPPortier]

What do you think about having the logger itself adding these formatting information ?

• this.logger: will know "it is" SDK -> it will add it when emitting log
• this.logger.debug: logger.debug function will know it is debug level then it will be added when emitting log

PROS:

• all calls to logger will be prefixed by same ... prefix
• all calls to logger./debug/info/..will have same prefix regarding log level
• all logs will have same pattern [Sinch SDK][level] and no human error to forgot them services will call logger function

[asein-sinch]

Done

[JPPortier]

❤️
May be adding some unit tests to ensure proper/format and log level.
Not sure we want to go to this direction for console logger and this PR, but other logging frameworks (e.g.: winston pointed by PR comment) are enabling to configure log level to not flood logs output/destination