Add support for preheat APIs

[kakkoyun]

Feature Request: Support for Harbor Preheat API Configuration

Is your feature request related to a problem? Please describe.

Currently, this provider does not support configuring the Harbor Preheat API. This feature would greatly enhance the ability to manage image preheating in Harbor projects, ensuring optimized performance and efficiency.

For more details, refer to the official Harbor documentation on preheating images: Harbor Preheat Images Documentation.

Describe the solution you'd like

I am keen to contribute by adding the necessary APIs for this feature. However, I would appreciate some guidance on how to move forward. Could you provide any pointers or resources to help me get started?

[flbla]

hi @kakkoyun,
thank you for the feature request.
we also need to manage preheat instances before we can create policies.

I started to implement the preheat instance

resource "harbor_preheat_instance" "example" {
  name       = "example-preheat-instance"
  vendor     = "dragonfly"
  endpoint   = "http://example.com"
  auth_mode  = "BASIC"
  username   = "example-user"
  password   = "example-password"
}

let me know if you want to implement preheat policy

[kakkoyun]

@flbla Thanks for the swift action! Awesome, I'll try this sometime this week and give you my feedback 🙏