Food processors and microwaves now respect food trays (#54927)

Really it's a bandaid as it would be better to wait until the refactor is done, but it turned out to be a rather easy fix.
Food trays may now once again mass insert both new and old food into the microwaves and food processors.

Prevents any manual handing when cooking large quantities of food at once.
Also, you get the switch gathering mode button when being given the serving tray again.

code/game/objects/structures/displaycase.dm

@@ -146,13 +146,7 @@
 				to_chat(user,  "<span class='notice'>You [open ? "close":"open"] [src].</span>")
 				toggle_lock(user)
 	else if(open && !showpiece)
-		if(showpiece_type && !istype(W, showpiece_type))
-			to_chat(user, "<span class='notice'>This doesn't belong in this kind of display.</span>")
-			return TRUE
-		if(user.transferItemToLoc(W, src))
-			showpiece = W
-			to_chat(user, "<span class='notice'>You put [W] on display.</span>")
-			update_icon()
+		insert_showpiece(W, user)
 	else if(glass_fix && broken && istype(W, /obj/item/stack/sheet/glass))
 		var/obj/item/stack/sheet/glass/G = W
 		if(G.get_amount() < 2)
@@ -167,6 +161,15 @@
 	else
 		return ..()
 
+/obj/structure/displaycase/proc/insert_showpiece(obj/item/wack, mob/user)
+	if(showpiece_type && !istype(wack, showpiece_type))
+		to_chat(user, "<span class='notice'>This doesn't belong in this kind of display.</span>")
+		return TRUE
+	if(user.transferItemToLoc(wack, src))
+		showpiece = wack
+		to_chat(user, "<span class='notice'>You put [wack] on display.</span>")
+		update_icon()
+
 /obj/structure/displaycase/proc/toggle_lock(mob/user)
 	open = !open
 	update_icon()
@@ -384,7 +387,6 @@
 	density = FALSE
 	max_integrity = 100
 	req_access = null
-	showpiece_type = /obj/item/reagent_containers/food
 	alert = FALSE //No, we're not calling the fire department because someone stole your cookie.
 	glass_fix = FALSE //Fixable with tools instead.
 	///The price of the item being sold. Altered by grab intent ID use.
@@ -577,3 +579,9 @@
 /obj/structure/displaycase/forsale/kitchen
 	desc = "A display case with an ID-card swiper. Use your ID to purchase the contents. Meant for the bartender and chef."
 	req_one_access = list(ACCESS_KITCHEN, ACCESS_BAR)
+
+/obj/structure/displaycase/forsale/insert_showpiece(obj/item/wack, mob/user)
+	if(!IS_EDIBLE(wack))
+		to_chat(user, "<span class='notice'>\The [src] smartly rejects [wack], as it only accepts food and drinks.</span>")
+		return TRUE
+	. = ..()