Check db startup and pass siginin error code

[lundibundi]

• Check DB connection status during startup
  otherwise we will get random unhandledRejection or 500 errors during API calls with errors like Password authentication failed for user with a long PG stacktrace

• Pass 403 error code in signin

[tshemsedinov]

Can we somehow detect connection status without a query?

[MarhiievHE]

To example, we can catch connection errors by manually creating connection using connect method from Pool:

await db.pg.pool.connect().catch((err) => {
....
});