The change includes:

• Added credentials to the HttpRequestInit interface
• Modified FetchBackend to pass the credentials option to the native fetch call
• Added unit tests to validate correct handling of the credentials option

Motivation / Use Cases

The credentials option is particularly useful for:

• Controlling whether cookies and HTTP authentication information are sent with requests ('omit', 'same-origin', 'include')
• Enabling proper CORS requests with credentials when needed
• Improving security and compliance with server authentication policies

Proposed Solution

• Add credentials to the HttpRequestInit interface
• Implement property handling in the HttpRequest class
• Pass the credentials option through FetchBackend to the native Fetch API
• Maintain backward compatibility by defaulting to existing behavior if not specified

Examples of New Usage

// GET request with credentials included
http.get('/api/user-data', {
  credentials: 'include'
}).subscribe();

Implementation Details / Compatibility Handling

• The credentials option is primarily read from the new req.credentials property.
• For backward compatibility, if req.withCredentials is true (legacy Angular option), credentials is set to 'include' ( override ).
• This ensures existing code using withCredentials continues to work as expected while enabling the new Fetch API credentials option.