Make SQLite3 the default database with a mounted volume

[pglombardo]

Since forever we've used PostgreSQL as the default and also support MariaDB/MySQL. This is really overkill for the majority of users.

With SQLite3 being used in production these days, I'd like to make it the default.

We would then have to update all documentation and docker-compose.yml files still specify that the application requires a mounted volume.

One requirement of this change would be that existing users who upgrade, we still respect their DATABASE_URL settings if they are using PostgreSQL or MariaDB/Mysql. Default when unspecified is SQLite3.

[didiermfb]

It should be cool if we can have a migration process to migrate from PostgreSQL to SQLite3 to keep the default.

[pglombardo]

Hi @didiermfb - I agree and I've thought about this a few times. I've filed #3808 to investigate and track progress.

[pglombardo]

SQLite3 is now the default database so we'll close this issue. We will investigate for an easy way to migrate from PostgreSQL to SQLite3 for existing users in #3808.

Thanks for the request & feedback!