Some model providers use short-lived api keys which must be renewed at regular intervals using another credential. For example, a GCP service account can be exchanged for an api key to call Vertex AI.
A StaticApiKey implementation is provided for API providers that use long lived api keys. OpenAiApi class was changed so that it accepts an ApiKey instead of a String which caused a lot small changes in downstream integration tests and auto configurations that were creating a OpenAiApi using a String key.
Model provider specific implementations of the ApiKey interface will be in a future commit.