fix: allow multiple user messages in a row for google gemini

[meronogbai]

Title:

• This will allow users to include multiple user messages in a row in gemini-pro.

Description: (optional)

• Inspired by this code

Motivation: (optional)

• An app I work on relies on multiple user messages and it was breaking for me when I tried to use it with gemini-pro.

How to test?

The following snippet breaks with gemini-pro even though it works with openai. Checkout this branch and everything should work without issues 🫡

async function main() {
  const stream = await openai.chat.completions.create({
    model: "gemini-pro",
    messages: ([
      {
        role: "user",
        content: "Say this is a test",
      },
      { role: "user", content: "now say im happy" },
    ]),
    stream: true,
    max_tokens: 4096,
  });

  for await (const chunk of stream) {
    process.stdout.write(chunk.choices[0]?.delta?.content || "");
  }
}

main();

[meronogbai]

Opting out in case of gemini-pro-vision because it doesn't support multiturn chat anyway.

[vrushankportkey]

Thank you so much for the PR, @meronogbai! This is amazing. Paging @VisargD who can check this

[VisargD]

Thanks for the PR @meronogbai . I will review and merge this PR today.

[VisargD]

LGTM. Closes #258