WorldGuard 6 support fails

[Sven65]

Bug details

Describe the bug

When starting a server with Slabbo and worldguard 6, the plugin fails to load.

To Reproduce

1. Install WG 6
2. Install Slabbo
3. Try to load the server
4. See error

Expected behavior

It should work as it does with WG 7.

Screenshots
If applicable, add screenshots to help explain your problem.

Runtime Configuration

Slabbo Version: 1.0.24

Server Software: Spigot

Server Version: 1.8.8

Other details

Additional context

[23:28:10 INFO]: [Slabbo] Loading Slabbo v1.0.24
[23:28:10 ERROR]: com/sk89q/worldguard/WorldGuard initializing Slabbo v1.0.24 (Is it up to date?)
java.lang.NoClassDefFoundError: com/sk89q/worldguard/WorldGuard
        at xyz.mackan.Slabbo.pluginsupport.WorldguardSupport.registerFlags(WorldguardSupport.java:26) ~[?:?]
        at xyz.mackan.Slabbo.Slabbo.onLoad(Slabbo.java:62) ~[?:?]
        at org.bukkit.craftbukkit.v1_8_R3.CraftServer.loadPlugins(CraftServer.java:297) [spigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-Spigot-db6de12-18fbb24]
        at net.minecraft.server.v1_8_R3.DedicatedServer.init(DedicatedServer.java:198) [spigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-Spigot-db6de12-18fbb24]
        at net.minecraft.server.v1_8_R3.MinecraftServer.run(MinecraftServer.java:525) [spigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-Spigot-db6de12-18fbb24]
        at java.lang.Thread.run(Unknown Source) [?:1.8.0_281]
Caused by: java.lang.ClassNotFoundException: com.sk89q.worldguard.WorldGuard
        at java.net.URLClassLoader.findClass(Unknown Source) ~[?:1.8.0_281]
        at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:101) ~[spigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-Spigot-db6de12-18fbb24]
        at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:86) ~[spigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-Spigot-db6de12-18fbb24]
        at java.lang.ClassLoader.loadClass(Unknown Source) ~[?:1.8.0_281]
        at java.lang.ClassLoader.loadClass(Unknown Source) ~[?:1.8.0_281]
        ... 6 more

The issue is due to changes in the WG API between WG6 and WG7.