Godot SDK and Blackholio tutorial

[lisandroct]

Description of Changes

Very small additions to the C# SDK specific for Godot.
I wrote the Godot Blackholio tutorial and updated the Unity one.
I added the image assets necessary for the tutorial.
I added the files for the Godot demo.

API and ABI breaking changes

No breaking changes.

Expected complexity level and risk

1. There's really no risk for current systems or projects, it's all new additions to support nicely(-ish) Godot, new Blackholio demo for Godot and updates to the tutorials.

Testing

• Follow the tutorial and verify everything works.
• Build for Windows and verify it works.
• Build for Linux and verify it works.
• Build SDK
• Publish to Nuget

[rekhoff]

I was only able to get part-way through docs/docs/00100-intro/00300-tutorials/00500-godot-tutorial/00300-part-2.md before hitting a blocker with the implementation.
The tutorial so far it looks good with only some minor nits, but the NuGet package issue will need to get addressed before I can finish reviewing.

[rekhoff]

I don't believe this will work to allow Godot to have code only relevant to it within the NuGet packages. Unity is able to get away with unique build flags because we have Unity developers Import the SpacetimeDB SDK using the C# SDK repo. This means for Unity developers, the original code is intact and constants like UNITY_5_3_OR_NEWER and UNITY_EDITOR are evaluated locally. Only the SpacetimeDB.BSATN.Codegen.dll and SpacetimeDB.BSATN.Runtime.dll are pre-built head of time.

When we publish the NuGet packages for the general C# developers, that will strip out the GODOT build flag because it's not included as a constant during compilation. If we did include it, that would make it available to all SDK users (which of course would break things since it's specifically imports using Godot.

We'll likely need another approch than using GODOT build flags, or would need to make a custom target framework specifically for this.

For additional context, if we follow the tutorial, but point at a local NuGet package build from the lisandro/godot-blackholio branch, we'd get the errors like:

GameManager.cs(43,23): Error CS0117 : 'AuthToken' does not contain a definition for 'TryGetToken'
GameManager.cs(49,9): Error CS0103 : The name 'STDBUpdateManager' does not exist in the current context

And again, this is because the code is getting stripped out.

[lisandroct]

I was wondering if this was going to work. I couldn't get my local NuGet working because I was missing what you dm me yesterday.
I guess the onlybest solution we have is to compile with the GODOT preprocessor flag and publish a different NuGet package.

[rekhoff]

In my most-recent testing, I was able to rebuild the NuGet packages with the SpacetimeDB.ClientSDK.Godot.2.1.0.nupkg package that is now getting generated.

[rekhoff]

I have tested the C# Server implementation instructions of the Godot tutorial and left my comments below.
I have also tested the client-godot version in the demo folder and confirmed it works as intended.

[rekhoff]

When creating this EntityController.cs script using Godot's Create Script dialog, you can't select Circle2D as what it Inherits from.
Since we aren't really asking them to define inheritance elsewhere and the code we copy in puts the correct inheritance in place anyway, this is just an optional thing.

If actually wanted them to be able to select our C# classes in this manner though, by having the Circle2D class defined with the [GlobalClass] attribute. Documentation around this is at https://docs.godotengine.org/en/4.4/tutorials/scripting/c_sharp/c_sharp_global_classes.html
With that in place, if we then press play once, so the project rebuilds, Circle2D shows up under Node2D as something that can be inherited from.

Since we don't actually ask them to do this, it would purely be for teaching users how to interact between the Godot Editor side of the house, and C# backend code that works with SpacetimeDB.

[rekhoff]

Suggested change

	```csharp
	public partial struct MoveAllPlayersTimer
	{
	```csharp
	[Table(Accessor = "move_all_players_timer", Scheduled = nameof(MoveAllPlayers), ScheduledAt = nameof(scheduled_at))]
	public partial struct MoveAllPlayersTimer
	{

Without this, we'll get an error on the C# step that reads

Add the following to your Init reducer to schedule the MoveAllPlayers reducer to run every 50 milliseconds.

[rekhoff]

Suggested change

	<AssemblyVersion>2.1.0</AssemblyVersion>
	<Version>2.1.0</Version>
	<AssemblyVersion>2.2.0</AssemblyVersion>
	<Version>2.2.0</Version>

As a note, we'll need to make sure the process we are using to update version numbers includes SpacetimeDB.ClientSDK.Godot.csproj going forward. Since that last update was pulled in from the master branch, the other NuGet packages are all on 2.2.0 while the Godot was still on 2.1.0