Add support for marking custom functions as deprecated with visual warnings

[danvervlad]

Summary

• Adds the ability to mark actions, conditions, and expressions as deprecated in extension functions
• Displays visual deprecation warnings in the Events Sheet when deprecated functions are used
• Allows extension authors to provide a deprecation message explaining what to use instead

Changes

Core/GDCore:

• Added SetDeprecationMessage and IsDeprecated methods to InstructionMetadata, ExpressionMetadata, and MultipleInstructionMetadata
• Added DeprecatedExpression error type to ExpressionParserError
• Extended InstructionValidator with ValidateParameter that returns both validity and deprecation status via new ParameterValidationResult struct
• Added deprecation fields to EventsFunction model (isDeprecated, deprecationMessage)

Events Sheet (UI):

• Displays [DEPRECATED] prefix for deprecated actions and conditions
• Shows deprecation message in tooltips
• Highlights deprecated expressions with visual styling (background highlight)
• Respects the existing showDeprecatedInstructionWarning preference flag

Extension Editor:

• Added "Deprecated" checkbox in function properties
• Added "Deprecation message" text field when function is marked deprecated

[danvervlad]

Function properties

With Deprecated = true

With Deprecated = false

With Show a warning on deprecated actions and conditions = true

In event sheet

In action/condition details

In expression details

With Show a warning on deprecated actions and conditions = false

In event sheet

In action/condition details

In expression details

[danvervlad]

In extension json, for serialization

[4ian]

Hello! Thanks for opening this PR.

The extension editor UI is still a bit rough today (the extension editor has changed a lot lately and we still try to improve it). The "Private" checkbox should have been named "Hidden": when you check it, you will see that existing usages of the function appear in yellow. So I wonder if this would have fitted your need?

More context: We try to make depreciation as transparent as possible for users. This means:

• "Deprecated" functions are never removed from reviewed extensions to ensure compatibility with old projects
• "Deprecated" functions are no longer visible to users when they add new actions, but the name of the new action is usually the same so they only notice that the list of parameter has changed

In your case, I guess you want to have the deprecation explanation shown to your users?
I will discuss this a bit more with the rest of the team.