db:dump - set connection name (so not only default_setup)

[Kudja]

Can be usefull to dump from slave or dump not only main DB if used more than 1 db in project

So when getting connection we can pass connection name to N98\Magento\DbSettings.php and use it instead of default, same time default must be default_setup + it as predefined param in constructor. Such way we'll not broke anything and we adding ability to dump stripped any DB used in project

[pocallaghan]

I'd imagine this is a relatively rare use case. Is this something you guys would be interested in having @tkn98? As one of the few people that actually does have multiple DBs, it's something that would be potentially useful to me, so I'm happy to take a crack at it. Presumably, if the feature does go ahead, it makes sense to add an optional argument for all DB related commands, defaulting to default_setup?

[ktomk]

In Magerun2 this has landed ca. 3 months ago (netz98/n98-magerun2#246) and just this morning I finished a first step of a bigger streamlining between the db:dump command in both versions. I still have to port DbSettings to Magento 2 which then would have a connectionType property which I think is this in Magento1, then we can backport this.

What you suggest looks similar to me to the PR in Magerun2, it's implemented via the AbstractDbCommand class and as far as I know it works well there. PRs are always welcome,

[tkn98]

This is also related to #890 in regard to command-line parameters.