[Feature] Allow Arbitrary Credentials From user_settings.json To Populate Credentials Model

[deeleeramone]

1. Why?:

   • Items defined in user_settings["credentials"] only populate if they are in the ProviderInterface, this is not ideal.

2. What?:

   • Populates the Credentials model with any leftover key:value pairs from user_settings.json, if it exists.

3. Impact:

   • Improved developer experience, more freedom.
   • Arbitrary keys being defined have no real consequence, but greatly improve the flexibility - like incorporating Hub configurations with completely custom APIs and apps that are authorized by a remote script.

4. Testing Done:

[piiq]

I was under the impression that we already support this, but then i realized that all my custom keys are the keys to custom providers that are defined as providers