Add entity source generation support for Durable Functions

[Copilot]

The source generator was not producing Azure Function triggers for entities when using the class-based syntax with [DurableTask] attribute, unlike orchestrators and activities which already had this support.

Changes

• DurableTaskSourceGenerator.cs: Added AddEntityFunctionDeclaration method that generates [EntityTrigger] function definitions for entity classes decorated with [DurableTask]
• AzureFunctionsTests.cs: Added 6 tests covering entity generation with primitive types, inheritance, custom state types, and mixed orchestrator/activity/entity scenarios

Example

Given:

[DurableTask(nameof(MyEntity))]
public class MyEntity : TaskEntity<int>
{
    public int Get() => this.State;
}

The generator now produces:

[Function(nameof(MyEntity))]
public static Task MyEntity([EntityTrigger] TaskEntityDispatcher dispatcher)
{
    return dispatcher.DispatchAsync<MyEntity>();
}

Original prompt

add durable function entity source generation support and tests properly

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[Copilot]

Pull request overview

This PR adds source generation support for Durable Task entities in Azure Functions scenarios. Previously, the source generator only produced function triggers for orchestrators and activities when using the class-based [DurableTask] attribute syntax. This change brings entities to feature parity by generating [EntityTrigger] function definitions.

Key Changes:

• Added AddEntityFunctionDeclaration method to generate entity trigger functions
• Added 4 comprehensive test methods covering primitive types, inheritance, custom state types, and mixed scenarios

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/Generators/DurableTaskSourceGenerator.cs	Added entity function generation logic in the Execute method and implemented the AddEntityFunctionDeclaration helper method following existing patterns
test/Generators.Tests/AzureFunctionsTests.cs	Added 4 test methods validating entity generation across different scenarios including primitive types, inheritance, custom state types, and mixed orchestrator/activity/entity usage