Implement login form for external application

[ernado-x]

For providing the ability for users to auth in to external applications by using an ecampus account we need to create a special login form.

This form should support the redirect back to the external application page and pass the authorisation code.

Route for login form: https://ecampus.kpi.ua/login/external

Query parameters which should handle form:

• redirect_uri
• appId

For auth user form should make POST request on endpoint: https://ecampus.kpi.ua/oauth/app/authorize
Structure of POST request:

public record ExternalApplicationAuthorizationRequest
{
    [Required] 
    public string Username { get; set; }

    [Required] 
    public string Password { get; set; }
    
    [Required] 
    public string AppId { get; set; }
    
    [Required] 
    public Uri RedirectUrl { get; set; }
}

If form received OK (200) response code from API, then it should redirect user back to external app and pass received authorisation code, form should be closed. In case of Forbid (403) response code – error message should be displayed for user.

This task should be implemented together with https://github.com/kpi-ua/api.campus.kpi.ua/issues/23