Document OPERATOR_TOKEN as required

[adam-beck]

- Summary

The documentation does not signal that the OPERATOR_TOKEN is required but the code indeed requires this.

- Test plan

Not Applicable

- Description for the changelog

Update Documentation regarding OPERATOR_TOKEN

- A picture of a cute animal (not mandatory but encouraged)

[adam-beck]

Unless I'm missing something (and I'm very new to Golang), it appears this line makes the OPERATOR_TOKEN required regardless if in multi-instance mode or not. I didn't see any way GlobalConfiguration wouldn't be used.

[kangmingtay]

Is there a reason why the OPERATOR_TOKEN is used to sign the token here instead of JWT_SECRET? It seems like regardless of whether gotrue is set to multi-instance mode or not, we use the operator token to sign the token when authenticating via external providers.

Thanks!