The model provider, e.g., 'amazon', 'cohere', 'ai21', etc. When not
supplied, provider is extracted from the first part of the model_id e.g.
'amazon' in 'amazon.titan-text-express-v1'. This value should be provided
for model IDs that do not have the provider in them, e.g., custom and provisioned
models that have an ARN associated with them.
