Fixes #3655 - prevent duplicate command registration

[MohabCodeX]

Fixes #3655
This PR makes addCommandHandler reject any duplicate command names whether they're in the same resource or across different ones. So if a command like "test" is already registered in one resource, trying to register it again (even in the same resource) will fail with a warning in debugscript 3. For example, if Resource A registers "kick", Resource B (or even A again) won’t be able to override it. It's a solid security improvement that ensures predictable command behavior and prevents hijacking or conflicts with minimal changes.
⚠️ Heads up: any existing resources with duplicate commands will now fail to register them so devs may need to audit and rename conflicting ones.

[ffsPLASMA]

I am against this PR, there are valid reasons to bind multiple functions to a single command.

[MegadreamsBE]

I am against this PR, there are valid reasons to bind multiple functions to a single command.

Should be configurable at the very least

[MohabCodeX]

I agree that sometimes multiple functions may need to be bound to the same command, but this can be handled better by combining them inside a single handler instead of registering several handlers for the same command which is bad practice in most cases.

Making this configurable per server is a good idea, and I can adjust the PR to support that.
Also, something like this should at least have a warning when duplicate handlers are added I know it's a breaking change if it refused the duplicated commands, but the warning would be important for catching accidental duplications.

Thanks for the feedback, I’ll make improvements.

[Fernando-A-Rocha]

Please make it configurable as this is trying to solve a problem that doesn't exist, imo.

I used to have a chatbox resource that, if I remember correctly, made use of multiple command handlers per command. Also there are cases in which you want the same command to be handled clientside and also serverside (idk if this PR considers this).

[Fernando-A-Rocha]

A warning on duplicate command handlers could be useful, I agree.
The config could be:
<allow_multi_command_handlers>
Values: 0, 1, 2
Where 0 is disallow, 1 is allow but with warning, and 2 is allow but no warnings.

[MohabCodeX]

Thank you for all the feedback

---

✅ Final Outcome: Configurable Duplicate Command Handler Behavior

A new server configuration option has been added:

<allow_multi_command_handlers>1</allow_multi_command_handlers>

This option controls how the system handles multiple addCommandHandler registrations for the same command.

Available Levels:

Value	Behavior	Debug Output
0	❌ Disallow duplicate command handlers	addCommandHandler: Duplicate command registration blocked for '%s' (multiple handlers disabled)
1 (default)	⚠️ Allow with warning	addCommandHandler: Attempt to register duplicate command '%s'
2	✅ Allow silently	(No debug output)

Default Behavior:

• The default value is 1, which allows duplicates but emits a warning, helping developers identify unexpected duplicate registrations.

Any other feedback would be appreciated.

[Fernando-A-Rocha]

Nice
When blocking duplicate command handlers I think it should throw a Lua error instead of a warning