Docs: unusable example on the better-auth usage meters docs

[dsfaccini]

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Description

To be brief, on this docs the example on the image is shown. I don't think this is usable because usage is metered server-side, and the authClient is imported client-side.

Reasoning

• Metered usage isn't like checkout products, you can call authClient.checkout({productId}) on the client and that will call the respective function in the server.
• In metered usage you're calling a service of some sort, like apiClient.get('new-ai-video') and the server must then call the service to create the video and ingest the usage based on that, like const { newAiVideo, tokensConsumed } = makeNewVideo(ctx.request); polar.usage.ingest('new-ai-video', { userId: <event.locals.auth.wheresThePolarUserId?>})
• Even if the authClient were to be used server-side, it has no context of the current user
  • (I could be wrong on this one but I don't think I am... the auth object server-side needs to get the user from the request token every time, and the authClient object client-side only keeps track of the respective cookie.)

// server-side
if (routeRequiresAuth(event)) {
    const session = await auth.api.getSession({
        headers: event.request.headers
    });
    event.locals.user = session.user;
}
// client-side
export const authClient = createAuthClient({
    plugins: [polarClient()]
});

Solution

• Add file names to the examples to make clear where they are used
• Update example to show server-side usage ingestion
• Add to example how to get the polar user ID from the server-side auth object (not authClient) to pass it to the polar.usage.ingest

Notes

• The better auth example I provided applies to all frameworks (it's in the better-auth section of the docs)
  • Idk if there are frameworks for which the server-side auth and client-side authClient sync, if this is the case please let me know.
• On sveltekit idk how to get the polar userId from the auth object.