[Bug]: Unable to create bedrock model without credentials

[mrh-chain]

What happened?

When adding a new model via the interface, if the provider is Bedrock, then one is required to add a set of AWS credentials. If LiteLLM is running on an AWS instance with an instance profile attached, then a set of static credentials isn't required. This can be demonstrated by clicking the "Test model" button with the AWS creds being blank.

Trying to save the model with them being blank results in an error. The fields should not be required.

Relevant log output

Are you a ML Ops Team?

No

What LiteLLM version are you on ?

v1.72.2

Twitter / LinkedIn details

No response

[wagnerjt]

Same as #8811.

You can do this programmatically which is what I do and you can see how in the issue