I ve been playing rugby for 10 years or so, I m spanish and we don't have a professional league here but still 6 of my team mates made the 7s team into the olympics so I have being able to look at various "pro programs", that plus 10 years of own lifting experience are my credentials.
First, you need to train movements not muscles, isolating them is a very commun mistake. People often look for a men's physique body with the strength of a powerlifter. This is not our goal, our goal is being able to transfer those gains into performance on the field as fast as possible. I could make a book out of this post, we could say lifting for rugby has been my life thesis inside the gym. But I will make it quick.
Your eating will depend on your position, if you are a forward you just have to take care of having an enough amount of protein to ensure your gains while if you are a back (my case) is more complicated because you need to make gains but without carrying too much fat, so I d suggest a high protein diet 2/3gr per kg. You will need to lift vigorously in every session, so dont forget to have a good source of carbs (white rice, potatoes) before hiting the gym or field practice while avoiding them the rest of the day.
In therms of lifting, while it is good to improve your maxiums this will mainly be a consequence of putting on more muscle mass. In the off season you will train as many times a week as possible because you dont have to care about doms annoying your field practice during in season time you have to take doms into consideration which means your main gains need to come in the off season, that's right, your bulking season will be in summer.
Okay, exercise time, your work must be, once again, around the main lifts. These exercises are a must for a rugby player: deadlift, squat variations, bench press, shoulder press, pull ups (as well as weighted) and row variations. Rep scheme could be 6x3 (85% of 1 rm) and focusing of performing the reps faster each week, don t get obsessed with the weight, change it just when it feels really light. There are still many things to be told about this but with this you will have a starting point.