[FR] Verify password server-side

**Is your feature request related to a problem? Please describe.**
I want to create a GraphQL API through which everything server-side is handled, including email-password authentication. Also, I want to make use of Firebase Authentication. I am able to register users with their email and password server-side, however, I am not able to verify their password when they are logging in through the GraphQL API, since the auth module of the node admin sdk does not support 'signing in', or checking the password in any other way server-side. I know I am able to recreate such a use case by letting the user login with the client side sdk, and after that, sending an id token to authenticate themselves, but that would require the client to have firebase installed, which is something I'd like to avoid.

**Describe the solution you'd like**
Something like `const userRecord = await auth().getUserByEmailAndPassword(email, password)` or `const isPasswordValid = await user.verifyPassword(password)`

**Describe alternatives you've considered**
Using an ID token sent from the client, but that would require you to install firebase on the client.

首先检查 Node Admin SDK 的 auth 模块及其支持的服务器端方法，然后将其与 Firebase Authentication client SDK 以及此处描述的 GraphQL API 流程进行比较。完成的要求是具备一种有文档说明且受支持的方式，可以在服务器端验证电子邮件和密码凭据，而无需在客户端使用 Firebase；在提出实现工作之前，请确认安全性和 API 约束。

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