Public backoff config to allow usage of WithAPIBackoff

[pipiland2612]

What Issue is this fixing ?

• Expose backoff directory so that we could use the function func WithAPIBackoff(cfg BackoffConfig) without the error: "Use of the internal package is not allowed"

Changes

• Create a BackoffConfig public struct that serve as a public layer to internal backoff.Config

[pipiland2612]

Another option is to define an interface that allows passing in the WithBackoff method. However, this approach feels less clean and adds unnecessary complexity for the client, since our goal is only to modify the configuration—not the underlying implementation.

[bwplotka]

Can you update title and description (and commit message)? It's out of date (description) and title is not human readable.

[bwplotka]

Amazing, looks good, just readability nits!