feat(vertexai/genai): add SystemInstruction

[jba]

Expose GenerateContentRequest.SystemInstruction.

As usual, put it on the Model, and use the Model field to construct
each request.

[eliben]

It'd be nice to have an example for this too.

Particularly because this is called "system prompt" everywhere else, and this may make it difficult for users to discover. For example, there's an issue on generative-ai-go asking for it: google/generative-ai-go#31

[jba]

Example forthcoming.

[jba]

I added a test and an example that shows various config options.
But I'm marking this a draft because the feature doesn't seem to be implemented.

[Deleplace]

But I'm marking this a draft because the feature doesn't seem to be implemented.

The Python sample for system instructions with Gemini 1.5 Pro is working for me. I'll see if I can get similar results with the Go sdk.

[Deleplace]

I'm getting compile errors at example_test.go, @jba can you PTAL?

[eliben]

I'm getting compile errors at example_test.go, @jba can you PTAL?

Is it a vet error? What does it say?

[Deleplace]

I'm getting compile errors at example_test.go, @jba can you PTAL?

Is it a vet error? What does it say?

% go test     
# cloud.google.com/go/vertexai/genai_test [cloud.google.com/go/vertexai/genai.test]
./example_test.go:58:38: undefined: option
./example_test.go:58:38: not enough arguments in call to genai.NewClient
	have (context.Context, unknown type)
	want (context.Context, string, string, ...option.ClientOption)
./example_test.go:58:56: undefined: os
FAIL	cloud.google.com/go/vertexai/genai [build failed]

And after fixing the imports:

./example_test.go:60:38: not enough arguments in call to genai.NewClient

The errors are trivial but I suspect we don't have jba's latest code.

[jba]

Sorry for the wait. I fixed the compilation problem and the feature now works with gemini-1.0-pro. Removing draft status.