I had our 17B rough wired for solar that I would install later. Like others have said, that amounts to running a black/red pair from the vicinity of the panel to somewhere behind the passenger side rear cabinet corner.
However, after further research, something obvious hit me. Namely that a) setting up camp in the shade is good for the trailer and me and b) although panels are really efficient these days in the shade, they always work much better in direct sun. I ended up getting portable panels from Solarland
and re-using the wire pair to wire a marine grade "troll motor" connector that I installed between the shore power (AC) connector and the water access. I also ordered their 10AWG 25' extension cable.
The 135W unit easily charges our dual 6V batteries and the 25' cable seems enough to get out of the shade (except in the deep redwoods). I recommend the marine connector (West Marine) and seal everything up with marine silicone sealer. I did a quick web search for this and there are a lot more options just two years later.