Don't know if you have room, but I use those brass 'quick-disconnect' hose fittings on all my fresh water hoses and connections.
I put one on the city water intake fitting and fit the matching fitting with a plug in it, into the intake while on the road to seal the connection from unwanted bugs, etc.
I carry an additional spare Q-D brass fitting to screw onto the water supply valve at the park when I'm hooking up...then it's simple to Q-D my hose to both the trailer and supply. I have several other spare hoses, so I can simply Q-D another if I need a longer length, etc.
I think there would be less 'strain' on that water inlet fitting on the trailer by just hooking and unhooking the pre-installed Q-D on the supply hose, as apposed to screwing/unscrewing a hose...or maybe you could permanently mount that 'spring' extension hose with some kind of rubber covered clamp - then put a Q-D fitting on the other end...to transfer the strain away from the valve assembly.
Ray & Pat; Morada, CA