auth.server.ts

```ts
/**
 * This plugin runs on the server and checks for the user's access token and
 * refresh token cookies.
 *
 * If one of them is missing, the user will be logged out and cookies will be
 * removed as a precaution.
 *
 * If both tokens are still valid, we get the user's account and log them in.
 *
 * If the access token has expired, we use the refresh token to get a new access
 * token, as wel as the account for the user and log them in.
 */

/* eslint-disable import/no-named-as-default-member */
// eslint-disable-next-line import/default
import jwt from 'jsonwebtoken'
import Cookie from 'cookie-universal'

export default defineNuxtPlugin(async (nuxtApp) => {
  const config = useRuntimeConfig()

  if (nuxtApp.ssrContext?.event) {
    const { setUser, removeUser } = useAuth()
    const cookie = Cookie(nuxtApp.ssrContext.event.req, nuxtApp.ssrContext?.event.res)
    const accessToken = cookie.get(config.cookieAccessToken)
    const refreshToken = cookie.get(config.cookieRefreshToken)
    const fifteenMinutes = 15 * 60 * 1000

    // Check if the refresh token is still valid, otherwise log the user out and
    // clean up the cookies.
    try {
      jwt.verify(refreshToken, useRuntimeConfig().jwtSecret)
    } catch (e) {
      removeUser()

      cookie.remove(config.cookieRefreshToken, {
        path: '/',
        httpOnly: true,
        sameSite: 'none',
        secure: true,
      })

      cookie.remove(config.cookieAccessToken, {
        path: '/',
        httpOnly: true,
        sameSite: 'none',
        secure: true,
      })

      return
    }

    // Check if the access token is still valid. If it is, get the user's
    // account and store it. If it's not, refresh the access token and log the
    // user in. When an issue occurs, log the user out and clean up the cookies.
    try {
      jwt.verify(accessToken, useRuntimeConfig().jwtSecret)

      // Decode the token to get the user's id.
      const decodedAccessToken = jwt.decode(accessToken)

      // Make sure the token contains a user id.
      if (typeof decodedAccessToken !== 'string' && decodedAccessToken?.id) {
        // Get the user's account.
        const data = await GqlGetAccount({ id: decodedAccessToken.id })

        setUser(data.getAccount)

        return
      }
    } catch (e) {
      const data = await GqlDoRefreshToken({ input: { refreshToken } })
      const accessToken = data.refreshToken?.accessToken

      const decodedAccessToken = jwt.decode(accessToken)

      // Create a new cookie for the access token.
      if (decodedAccessToken) {
        cookie.set(config.cookieAccessToken, accessToken, {
          path: '/',
          httpOnly: true,
          sameSite: 'none',
          secure: true,
          expires: new Date(Date.now() + fifteenMinutes),
        })
      }

      // Make sure the token contains a user id.
      if (typeof decodedAccessToken !== 'string' && decodedAccessToken?.id) {
        // Get the user's account.
        const data = await GqlGetAccount({ id: decodedAccessToken.id })

        setUser(data.getAccount)

        return
      }

      // Things went wrong, so remove the user and clean up the cookies.
      removeUser()

      cookie.remove(config.cookieRefreshToken, {
        path: '/',
        httpOnly: true,
        sameSite: 'none',
        secure: true,
      })

      cookie.remove(config.cookieAccessToken, {
        path: '/',
        httpOnly: true,
        sameSite: 'none',
        secure: true,
      })
    }
  }
})
```