I've done it with a 2010 RAV4 Sport. Bought the Toyota 4 pin wiring harness (instructions)
on line (cheaper than from my dealer), almost broke my neck finding the location under the dash to plug the front connector.
I used the information from this web page
to run the additional wiring at the same time I ran the Toyota harness. I pretty much followed the web page, but added the wiring for a back up camera (for both the RAV4 & the trailer) at the same time. I used a Tekonsha Prodigy P3
controller mounted as shown on the web page. If you want to read about my antics running the wiring, check my Nantucket page
I wrote while doing the project. #6 wire from the battery to the breaker panel under the glove box, then #12 for the brake controller & #10 for the charge line. Finding a place for the 50 amp fuse in the engine compartment near the battery was probably the most difficult part, although there are a lot of panels to remove & replace to make the run from the front to the back.
I didn't use a 4 pin to 7 pin adapter; used a sealed 7 pin connector & spliced the Toyota harness wires to the correct ones on the 7 pin connector. I prefer the sealed version of the 7 pin connector to the back wired versions - less chance of water getting into the works.
I also added a solenoid in the space above the driver's side rear tire well in the charging circuit. It is powered by the 12V receptacle in the same location so that it shuts off the charge line when the RAV4 isn't running. This is useful for preventing killing the tow vehicle battery when parked & running the refrigerator on 12V...