Melt the coconut oil in a large pot over medium heat and saute the onion until it's tender, about 8 minutes. Add in the garlic and spinach, and stir until the spinach is wilted. Use a fork to scrape the cooked spaghetti squash flesh into pot and pour the enchilada sauce over the top. Stir well until everything is heated through, season to taste, and then divide the cooked vegetables between the two shells of the spaghetti squash arranged cut-side-up on a baking sheet. (Alternatively, you can just use two oven-safe serving dishes, if you'd prefer.) Top each serving with shredded goat cheddar, and place the baking sheet under your oven's broiler, set to high, for about 3 minutes, or until the cheese is melted and bubbly. Serve warm.