Missing example: structured output with Custom Model Import (CMI)

[manuwaik]

Problem

The custom-models/ directory has examples for fine-tuning, distillation, and importing models, but nothing showing how to use Bedrock's structured output (response_format with a JSON schema) against a CMI model.

CMI supports OpenAIChatCompletion, OpenAICompletion, and BedrockCompletion request shapes, and the response_format parameter varies between them — this is a common source of confusion when adapting foundation-model code to imported models.

Proposal

Add a notebook under custom-models/ that:

• Demonstrates schema-constrained generation against a CMI model via InvokeModel using OpenAIChatCompletion.
• Uses Pydantic to define the schema as a single source of truth for both the response_format constraint and downstream validation.
• Shows the contrast vs. prompted-JSON (baseline) so readers understand what schema enforcement buys them.

References

• Structured outputs for imported models
• Invoke an imported model

PR #710 implements this.