Support Pardot API v4

[sminnee]

Pardot now has a v4 API, and new accounts don't seem to work with the v3 API. It would be great if the v4 API was supported by this package.

[hglattergotz]

Hi @sminnee! Thanks for bringing that to my attention. Would you be willing to help?
I no longer have access to a pardot account, but could help with concepts and reviews.

[davejtoews]

I've been able to make use of this library using version 4 just by changing the version property in the Connector class. All I'm using is the form query and form read endpoints, so I can't say that this library is 100% compatible with version 4, but it works well enough for me.

[grgcnnr]

The v4 api is mostly the same as far as I can see. The big difference is that multiple prospects can have the same email address so you can no longer use that as a primary key.

E.g you can no longer assign visitors to prospects by email address.
You have to first get prospect(s) by email address, grab their ID then assign the visitor to the prospect via ID. Just be careful what params you pass and you should be fine.

[hglattergotz]

@grgcnnr PR #5 is pending for v4, but I was lacking context, which you now have provided. Any chance you could help out with getting this over the finish line?

[grgcnnr]

@hglattergotz ive only just started an integration using pardot so will let you know how I go.

This PR looks fine especially since you can pass the version to the constructor right?

@sminnee @davejtoews you should be able to pass version in as a parameter when you instantiate Connector

[grantbrokergenius]

Any chance of getting a release for this change? I'm using dev-master in composer to get v4 to work, but would prefer to not have to use that.