Add tests for orchestrator response with text generation edge cases

[evaline-ju]

Description

As an orchestrator developer, I want to confirm that the orchestrator responds as expected if any text generation servers do not respond with text or all whitespace text or potentially other edge cases.

Discussion

Add unit tests with mock results from text generation clients returning no text (say just a stop token), all whitespace text, etc.

Acceptance Criteria

• Unit tests cover new/changed code
• Examples build against new/changed code
• READMEs are updated
• Type of semantic version change is identified

[flaviabeo]

Hi! Can you assign me on this one?