Implement Basic Authentication for Operaton Client

[kren-prog]

Description:

Currently, the Operaton client communicates with the API without any authentication, which serves for local implementation. However, for staging or production poses a security risk. This issue addresses the need to implement basic authentication to ensure that all requests are properly secured.

Proposed Solution

• Update the BaseOperatonClient to include username and password attributes.
• Use these credentials to add a Basic Authentication header to all API requests.
• Refactor the ExternalTaskClient and ProcessClient to support and utilize the new authentication
  mechanism.

This will ensure that all interactions with the Operaton API are authenticated, enhancing the overall security of the integration.