Add cause to PlayerOpenSignEvent (#9441)

Also fire the event for plugin-opened signs

patches/api/Add-event-for-player-editing-sign.patch

@@ -18,6 +18,7 @@ index 0000000000000000000000000000000000000000..00000000000000000000000000000000
 +import org.bukkit.event.Cancellable;
 +import org.bukkit.event.HandlerList;
 +import org.bukkit.event.player.PlayerEvent;
++import org.jetbrains.annotations.ApiStatus;
 +import org.jetbrains.annotations.NotNull;
 +
 +/**
@@ -28,13 +29,16 @@ index 0000000000000000000000000000000000000000..00000000000000000000000000000000
 +public class PlayerOpenSignEvent extends PlayerEvent implements Cancellable {
 +    private static final HandlerList HANDLER_LIST = new HandlerList();
 +    private boolean cancel = false;
-+    @NotNull private final Sign sign;
-+    @NotNull private final Side side;
++    private final Sign sign;
++    private final Side side;
++    private final Cause cause;
 +
-+    public PlayerOpenSignEvent(@NotNull Player editor, @NotNull Sign sign, @NotNull Side side) {
++    @ApiStatus.Internal
++    public PlayerOpenSignEvent(final @NotNull Player editor, final @NotNull Sign sign, final @NotNull Side side, final @NotNull Cause cause) {
 +        super(editor);
 +        this.sign = sign;
 +        this.side = side;
++        this.cause = cause;
 +    }
 +
 +    /**
@@ -58,6 +62,15 @@ index 0000000000000000000000000000000000000000..00000000000000000000000000000000
 +        return side;
 +    }
 +
++    /**
++     * The cause of this sign open.
++     *
++     * @return the cause
++     */
++    public @NotNull Cause getCause() {
++        return cause;
++    }
++
 +    @Override
 +    public boolean isCancelled() {
 +        return cancel;
@@ -78,4 +91,26 @@ index 0000000000000000000000000000000000000000..00000000000000000000000000000000
 +    public static HandlerList getHandlerList() {
 +        return HANDLER_LIST;
 +    }
++
++    /**
++     * The cause of the {@link PlayerOpenSignEvent}.
++     */
++    public enum Cause {
++        /**
++         * The event was triggered by the placement of a sign.
++         */
++        PLACE,
++        /**
++         * The event was triggered by an interaction with a sign.
++         */
++        INTERACT,
++        /**
++         * The event was triggered via a plugin with {@link org.bukkit.entity.HumanEntity#openSign(Sign, Side)}
++         */
++        PLUGIN,
++        /**
++         * Fallback cause for any unknown cause.
++         */
++        UNKNOWN,
++    }
 +}