Use int for CandidateCount

[rakyll]

It's very likely that users will hardcode the candidate count at a call site such as:

s.client.Models.GenerateContentStream(
     stream.Context(),
     s.config.Model,
     parts,
     &genai.GenerateContentConfig{CandidateCount: genai.Ptr(int64(5))})

In Go, it's more idiomatic to rely on int especially when it's clear that you don't need 64-bits. If candidate count was an int, it feels more natural to write without having to cast to int64:

s.client.Models.GenerateContentStream(
     stream.Context(),
     s.config.Model,
     parts,
     &genai.GenerateContentConfig{CandidateCount: genai.Ptr(5)})

[rakyll]

We can omit the use of pointers for this field, and make it look like:

type GenerateContentConfig struct {
        ...
	CandidateCount int  `json:"candidateCount,omitempty"`
	...
}

[happy-qiao]

I'm on it! Just need to fix some testing magic first.

[eliben]

We can omit the use of pointers for this field, and make it look like:

type GenerateContentConfig struct {
        ...
	CandidateCount int  `json:"candidateCount,omitempty"`
	...
}

What is the meaning of a default value (0) on CandidateCount?

[happy-qiao]

Depends on Backend. GoogleAI throws 400 error but VertexAI return 1 candidate response

[eliben]

There should be consistent behavior for the user here, I think. We should be careful to distinguish between "not set" and "explicitly asked 0" -- the latter can result in an error, for example (*). Therefore pointers could definitely be useful here.

(*) An error is always a good start, because it can be removed later and replaced by different behavior. If we start with different behavior, turning it into an error later is impossible if we want to retain backwards compatibility.

[happy-qiao]

How about using value type for candidate_count and overwrite the default 0 to 1? This can ensure the same behavior for the two backends as well as a smooth user journey.

[happy-qiao]

CandidateCount is now value type. When CandidateCount is zero value, the SDK will overwrite the value to 1