Draft: LLM Observability

[langchain4j]

Issue

#199

Change

• Added ChatLanguageModelListener, ChatLanguageModelRequest, and ChatLanguageModelResponse that are compatible (have all the required attributes) with OTEL LLM semconv draft.
• Added an option to attach ChatLanguageModelListener to OpenAiChatModel and OpenAiStreamingChatModel (pilot module)

General checklist

• There are no breaking changes
• I have added unit and integration tests for my change
• I have manually run all the unit and integration tests in the module I have added/changed, and they are all green
• I have manually run all the unit and integration tests in the core and main modules, and they are all green
• I have added/updated the documentation
• I have added an example in the examples repo (only for "big" features)

[langchain4j]

@brunobat could you please take a look? 🙏

[geoand]

I'm also very interested in this so we can augment in the already present observability features in the Quarkus implementation.

I also think that having something like this in sooner that rather than later would be very helpful as these new integration points could definitely prove useful for various tasks.

[geoand]

I believe that onResponse could also be passed ChatLanguageModelRequest

[langchain4j]

@geoand yeah I was just adding it :)

[geoand]

💪🏼

[langchain4j]

@geoand do you think id can still be useful for something (after adding request to onResponse())?

[geoand]

I very much doubt it's useful