Move tokens to "secrets" table

[lalalune]

We are using bearer token auth for authenticating the calls out of the database. There is a pg function that calls after messages are sent and one after accounts are created, both use an HTTP post and have the bearer hardcoded.

Instead, the bearer should be in a table and dynamically loaded into the function.

Finally, we need to update the README to indicate how the user populates the initial secrets.