Implement Auth0 middleware in the API

[ygrishajev]

Recently we allowed credentials to be sent to the server be able to utilize cloudflare protections. This made possible to send cookies to the server. In turn this makes auth proxy redundant. We need to add similar logic to auth middleware on the api to be able to get rid of the proxied requests.

Acceptance criteria:

• api auth middleware is able to verify a user by auth0 session cookie
• /v1/start-trial is not proxied when user is logged in
• /v1/start-trial sends the cookies to the API