Add support for structured output in Ollama

[andreadimaio]

This PR enables the use of structured output with json_schema in Ollama.

My idea is to force the use of the structured output + json_schema every time an AIService returns a POJO and the developer doesn't fill the "format" property. In this second case, the value chosen by the developer will have the priority.

[quarkus-bot]

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It should be safe to merge provided you have a look at the other checks in the summary.

[geoand]

Thanks a lot!

[andreadimaio]

I realize that I can improve the format checks a bit at build time, but before I start adding those checks, let me know what you think.

Today, the format property can take the value json or a json object that must conform to a json-schema {...}.

Suppose we have an AIService that returns a Person object and the format property has the value

• null | empty: The json schema is automatically generated and used by quarkus.
• json: The structured output is not used and the string "You must..." is appended to the prompt.
• {...} (a manual json schema is provided. I don't know how often this can happen, but it could):
  • json-schema invalid: raises an exception.
  • json-schema matches the Person object: continue without exception.
  • json-schema doesn't match the Person object: throws an exception, or we have to use whatever the developer wrote?

What do you think about these checks.. do they make sense or I'll increase the lines of code without giving a value?

My doubt is what to do when the developer writes a correct json-schema in the format property?

[geoand]

The way things are now with my initial commit, both the json_schema and the old You must... are captured at build time and available at runtime to the AiService implementation.

I believe that initially we should default to the latter for now, while allowing the users to opt-in to the new structured output (like the test I had added does). In the future we can flip that default.
To be honest, I don't see a scenario where the user writes the schema themselves.

[andreadimaio]

To be honest, I don't see a scenario where the user writes the schema themselves.

I think so too 👍 . Let's see if some future issues show us if other developers think differently.

[geoand]

We'll find out soon enough :)