Set source property on TNTPrimed entities.

This property makes TNT explosions look more "real" to other plugins who
may be consuming events from MobArena's sessions. It also gives way to a
potential rework of the "planter" logic that currently makes use of the
Bukkit Metadata API.

Closes #718

changelog.md

@@ -38,6 +38,7 @@ These changes will (most likely) be included in the next version.
 - Players no longer take fall damage when they leave (or get removed from) an arena while falling.
 - Players no longer take damage from projectiles shot by pets of other players.
 - MobArena no longer nags players with the `mobarena.admin.teleport` permission when they engage in a teleport that would have otherwise been blocked.
+- MobArena now correctly sets the source property on auto-ignited TNT.
 
 ## [0.106] - 2021-05-09
 ### Added

src/main/java/com/garbagemule/MobArena/ArenaListener.java

@@ -286,6 +286,7 @@ public class ArenaListener
                 }
                 stack.setAmount(stack.getAmount() - 1);
                 TNTPrimed tnt = b.getWorld().spawn(b.getRelative(BlockFace.UP).getLocation(), TNTPrimed.class);
+                tnt.setSource(event.getPlayer());
                 setPlanter(tnt, event.getPlayer());
                 return;
             }
@@ -364,6 +365,7 @@ public class ArenaListener
                         if (planter != null) {
                             b.setType(Material.AIR);
                             TNTPrimed tnt = b.getWorld().spawn(b.getLocation(), TNTPrimed.class);
+                            tnt.setSource(planter);
                             setPlanter(tnt, planter);
                         }
                     } else {