Making drivers pluggable

[DullReferenceException]

I really like the feature set of orm2 and wish I could use it for our application, which has a Cassandra database. My colleagues and I have discussed the option of developing a driver for Cassandra. However, integrating such a thing directly into this repository may be a big distraction as we iterate on and improve said driver.

There may be a way to hack together a plugin that extends orm2, but what would be most ideal is if orm2 allowed you to add external drivers in a documented way. Something like this:

var orm = require('orm2');
orm.addDriver('cassandra', CassandraDriver);

It looks like drivers are already close to being externalizable, but I think a little work is necessary to make this user-friendly.

Are you open to enabling external drivers for orm2? And if you haven't already started an effort toward this, would you welcome pull requests for enabling this functionality?

[DullReferenceException]

I've created this pull request to support this enhancement. Please let me know if you have any feedback.

[dxg]

This sounds interesting.
I've had a look at the pull request, and so far it looks much simpler than I expected (which is a good thing).

I've been thinking about the overall architecture and I also want to make it easier to add new drivers.

The solution I've been thinking about involves renaming Drivers to Adapters (since in node world, packages such as pg & mysql are considered drivers. This would avoid any confusion.

The other thing I'd like to do is move the current drivers out of ORM & into their own individual packages. The suggested orm.addDriver (or orm.addAdapter) API change would be used for this also. This wouldn't really change anything for your driver, but I think it may make things more consistent.

What do you think of the driver -> adapter name change, and driver move overall?

Besides that, the code looks good & I'm happy to merge once I get some input on my suggested changes as they may impact the addDriver function name.

[DullReferenceException]

Thanks for your feedback. I like your suggestion to rename Drivers to Adapters and will make that change in my pull request.

[DullReferenceException]

OK, I have done a bunch of renaming, and apparently not everything can be safely renamed from driver to adapter. The test breakage I encountered was that sql-ddl-sync reads a driver property from the options passed to Sync. Plus, I think according to the documents there's a driver property accessed in one of the code examples, so that should probably be considered as part of the public interface.

It's probably best if I stick to just renaming addDriver to addAdapter for now (and updating the documents).

[DullReferenceException]

Pull request is updated and ready for review.

[dxg]

Sounds good. I'll make the other changes later where possible.

[dxg]

Merged.