Gson date serialization is locale-specific

[GiantTreeLP]

Gson serializes and deserializes dates based on locale. This can cause issues like the following stacktrace.

We should change the default settings in Gson but upgrading may require a custom type adapter.

com.google.gson.JsonSyntaxException: Jan 6, 2020, 9:39:24 AM
	at com.google.gson.internal.bind.DateTypeAdapter.deserializeToDate(DateTypeAdapter.java:74) ~[spigot.jar:git-Spigot-1a3504a-84f3da3]
	at com.google.gson.internal.bind.DateTypeAdapter.read(DateTypeAdapter.java:59) ~[spigot.jar:git-Spigot-1a3504a-84f3da3]
	at com.google.gson.internal.bind.DateTypeAdapter.read(DateTypeAdapter.java:41) ~[spigot.jar:git-Spigot-1a3504a-84f3da3]
	at com.google.gson.internal.bind.TypeAdapters$26$1.read(TypeAdapters.java:598) ~[spigot.jar:git-Spigot-1a3504a-84f3da3]
	at com.google.gson.internal.bind.TypeAdapters$26$1.read(TypeAdapters.java:596) ~[spigot.jar:git-Spigot-1a3504a-84f3da3]
	at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.read(ReflectiveTypeAdapterFactory.java:129) ~[spigot.jar:git-Spigot-1a3504a-84f3da3]
	at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:220) ~[spigot.jar:git-Spigot-1a3504a-84f3da3]
	at com.google.gson.Gson.fromJson(Gson.java:887) ~[spigot.jar:git-Spigot-1a3504a-84f3da3]
	at com.google.gson.Gson.fromJson(Gson.java:952) ~[spigot.jar:git-Spigot-1a3504a-84f3da3]
	at de.dytanic.cloudnet.lib.utility.document.Document.getObject(Document.java:423) ~[CloudNetAPI.jar:2.1.17]
	at de.dytanic.cloudnet.api.network.packet.in.PacketInLogoutPlayer.handleInput(PacketInLogoutPlayer.java:25) ~[CloudNetAPI.jar:2.1.17]
	at de.dytanic.cloudnet.lib.network.protocol.packet.PacketManager$2.run(PacketManager.java:99) ~[CloudNetAPI.jar:2.1.17]
	at de.dytanic.cloudnet.lib.network.protocol.packet.PacketManager$2.run(PacketManager.java:92) ~[CloudNetAPI.jar:2.1.17]
	at de.dytanic.cloudnet.lib.utility.CollectionWrapper.iterator(CollectionWrapper.java:61) ~[CloudNetAPI.jar:2.1.17]
	at de.dytanic.cloudnet.lib.network.protocol.packet.PacketManager.dispatchPacket(PacketManager.java:92) ~[CloudNetAPI.jar:2.1.17]
	at de.dytanic.cloudnet.lib.network.NetDispatcher$1.run(NetDispatcher.java:66) ~[CloudNetAPI.jar:2.1.17]
	at de.dytanic.cloudnet.lib.scheduler.TaskScheduler$VoidTaskEntry$1.call(TaskScheduler.java:585) ~[CloudNetAPI.jar:2.1.17]
	at de.dytanic.cloudnet.lib.scheduler.TaskScheduler$VoidTaskEntry$1.call(TaskScheduler.java:579) ~[CloudNetAPI.jar:2.1.17]
	at de.dytanic.cloudnet.lib.scheduler.TaskEntry.invoke(TaskEntry.java:33) ~[CloudNetAPI.jar:2.1.17]
	at de.dytanic.cloudnet.lib.scheduler.TaskScheduler$Worker.execute(TaskScheduler.java:527) [CloudNetAPI.jar:2.1.17]
	at de.dytanic.cloudnet.lib.scheduler.TaskScheduler$Worker.run(TaskScheduler.java:490) [CloudNetAPI.jar:2.1.17]
Caused by: java.text.ParseException: Failed to parse date ["Jan 6, 2020, 9:39:24 AM']: Invalid number: Jan 
	at com.google.gson.internal.bind.util.ISO8601Utils.parse(ISO8601Utils.java:274) ~[spigot.jar:git-Spigot-1a3504a-84f3da3]
	at com.google.gson.internal.bind.DateTypeAdapter.deserializeToDate(DateTypeAdapter.java:72) ~[spigot.jar:git-Spigot-1a3504a-84f3da3]
	... 20 more
Caused by: java.lang.NumberFormatException: Invalid number: Jan 
	at com.google.gson.internal.bind.util.ISO8601Utils.parseInt(ISO8601Utils.java:311) ~[spigot.jar:git-Spigot-1a3504a-84f3da3]
	at com.google.gson.internal.bind.util.ISO8601Utils.parse(ISO8601Utils.java:129) ~[spigot.jar:git-Spigot-1a3504a-84f3da3]
	at com.google.gson.internal.bind.DateTypeAdapter.deserializeToDate(DateTypeAdapter.java:72) ~[spigot.jar:git-Spigot-1a3504a-84f3da3]
	... 20 more

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[juliarn]

Changing the date format with the GsonBuilder should solve this issue.