Rinse and dry the chicken thoroughly. Cut off any lumps of fat. Put one bouillon cube inside the cavity. Squeeze the lemon, reserving the juice. Put the lemon rinds in the cavity. Put the chicken in the slow cooker, breast side up, and sprinkle with the paprika and parsley. Distribute the onion wedges and garlic around the chicken. Pour over the soy sauce and lemon juice and season with the salt and pepper. Crumble the remaining bouillon cube, and sprinkle that over the chicken as well. Top with the potatoes and mushrooms. Cover and cook on HIGH 3 1/2 to 4 1/2 hours.