* dburl.nim: simpler regex that can support db_urls with . and - in hostname
* dbrul.nim: accepting any non-empty sequence for user and password
* dburl.nim: skipping validation for 'sqlite' db paths
It starts an asynchronous infinite task that checks the connectivity
with the database. In case of error, the postgres_healthcheck task
tries to reconnect for a while, and if it determines that the connection
cannot be resumed, then it invokes a callback indicating that
situation. For the case of the `wakunode2` app, this callback
quits the application itself and adds a log trace indicating
the connectivity issue with the database.
* Refactoring the Waku Archive. Simplifying the app.nim
This change is needed to accommodate the further PRs where we will integrate Postgres in `wakunode2`.