Make auto_registration more flexible

[solnic]

Currently ROM::Configuration#auto_registration supports :namespace option but it is only an on/off toggle, when it's turned on, then the first directory under provided path is treated as the namespace, then we assume there are relations, commands and mappers sub-dirs under that namespace dir. ie auto_registration('lib/persistence', namespace: true) will look for lib/persistence/(relations|mappers|commands)/**/*.rb and assumes module hierarchy is Persistence::(Relations|Mappers|Commands::*.

So, it'd be nice to make it more flexible, so that we can do this:

• auto_registration('lib/persistence', namespace: true) - current behavior is maintained
• auto_registration('lib/persistence', namespace: false) - current behavior is maintained
• auto_registration('lib/persistence', namespace: 'MyApp::MyPersistence') - a string can be set as the namespace, in which case the root dir name is not going to be used as the namespace. So it's gonna load lib/persistence/(relations|mappers|commands)/**/*.rb and assume that things are defined under MyApp::MyPersistence namespace ie lib/persistence/relations/users == MyApp::MyPersistence::Relations::Users

/cc @janjiss

Closes #338

[solnic]

There's also #331 that wasn't finish, we could probably make it completely flexible by allowing passing a custom dir/constant resolver

[janjiss]

@solnic Wondering about the api for custom dir/constant resolver. Do you think we should add another parameter or change existing one :namespace to allow custom resolver? If we use the same parameter name, can we have some kind of type that has to inherit from base strategy?

[solnic]

Let's hold off with any further improvements until somebody asks for something more customized, then we can revisit.

[wmaciejak]

Hi @solnic ! I wrote some months ago about my case on gitter. I don't like classic separation components by type (f.e. directories app/relations/users.rb, analogical mappers and commands) because IMO better, more efficient way is separation by business feature(f.e. app/contexts/user/relation.rb, app/contexts/post/relation.rb). I created one, quite big project with that approach and it saved my life(and common sense :D ). I used ROM v1, and created a custom registration of components cause that kind of directories configuration was unsupported.

I wonder if there is a way to smart auto-register components in that configuration or maybe it's so significant difference between approaches?