feat: Add Hook Dependency Injection extension method with Hook instance (#513)

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## This PR
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In #512 I needed to tweak the sample AspNetCore application to pass Hook
options to the MetricsHook. I noticed that in order to pass the options
I needed to use the delegate based approach, while discarding the
`serviceProvider`, like:

```csharp
featureBuilder.AddHostedFeatureLifecycle()
        .AddHook(_ => new MetricsHook(metricsHookOptions))
```

It would be simpler and easier for devs to interact with a third
overload that allows them to pass an instance of the hook that they want
to interact with, like so:

```csharp
featureBuilder.AddHostedFeatureLifecycle()
    .AddHook(new MetricsHook())
```

### Related Issues
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### Notes
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### Follow-up Tasks
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noted under this section -->
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### How to test
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---------

Signed-off-by: Kyle Julian <38759683+kylejuliandev@users.noreply.github.com>

Author: kylejuliandev

README.md

@@ -481,6 +481,7 @@ builder.Services.AddOpenFeature(featureBuilder => {
         .AddHostedFeatureLifecycle()
         .AddContext((contextBuilder, serviceProvider) => { /* Custom context configuration */ })
         .AddHook((serviceProvider) => new LoggingHook( /* Custom configuration */ ))
+        .AddHook(new MetricsHook())
         .AddInMemoryProvider("name1")
         .AddInMemoryProvider("name2")
         .AddPolicyName(options => {

src/OpenFeature.DependencyInjection/OpenFeatureBuilderExtensions.cs

@@ -278,6 +278,33 @@ public static OpenFeatureBuilder AddHook<THook>(this OpenFeatureBuilder builder,
         return builder.AddHook(typeof(THook).Name, implementationFactory);
     }
 
+    /// <summary>
+    /// Adds a feature hook to the service collection. Hooks added here are not domain-bound.
+    /// </summary>
+    /// <typeparam name="THook">The type of<see cref="Hook"/> to be added.</typeparam>
+    /// <param name="builder">The <see cref="OpenFeatureBuilder"/> instance.</param>
+    /// <param name="hook">Instance of Hook to inject into the OpenFeature context.</param>
+    /// <returns>The <see cref="OpenFeatureBuilder"/> instance.</returns>
+    public static OpenFeatureBuilder AddHook<THook>(this OpenFeatureBuilder builder, THook hook)
+        where THook : Hook
+    {
+        return builder.AddHook(typeof(THook).Name, hook);
+    }
+
+    /// <summary>
+    /// Adds a feature hook to the service collection with a specified name. Hooks added here are not domain-bound.
+    /// </summary>
+    /// <typeparam name="THook">The type of<see cref="Hook"/> to be added.</typeparam>
+    /// <param name="builder">The <see cref="OpenFeatureBuilder"/> instance.</param>
+    /// <param name="hookName">The name of the <see cref="Hook"/> that is being added.</param>
+    /// <param name="hook">Instance of Hook to inject into the OpenFeature context.</param>
+    /// <returns>The <see cref="OpenFeatureBuilder"/> instance.</returns>
+    public static OpenFeatureBuilder AddHook<THook>(this OpenFeatureBuilder builder, string hookName, THook hook)
+        where THook : Hook
+    {
+        return builder.AddHook(hookName, _ => hook);
+    }
+
     /// <summary>
     /// Adds a feature hook to the service collection using a factory method and specified name. Hooks added here are not domain-bound.
     /// </summary>

test/OpenFeature.DependencyInjection.Tests/OpenFeatureBuilderExtensionsTests.cs

@@ -302,6 +302,40 @@ public void AddHook_WithSpecifiedNameAndImplementationFactory_AsKeyedService()
         Assert.NotNull(hook);
     }
 
+    [Fact]
+    public void AddHook_WithInstance_AddsHookAsKeyedService()
+    {
+        // Arrange
+        var expectedHook = new NoOpHook();
+        _systemUnderTest.AddHook(expectedHook);
+
+        var serviceProvider = _services.BuildServiceProvider();
+
+        // Act
+        var actualHook = serviceProvider.GetKeyedService<Hook>("NoOpHook");
+
+        // Assert
+        Assert.NotNull(actualHook);
+        Assert.Equal(expectedHook, actualHook);
+    }
+
+    [Fact]
+    public void AddHook_WithSpecifiedNameAndInstance_AddsHookAsKeyedService()
+    {
+        // Arrange
+        var expectedHook = new NoOpHook();
+        _systemUnderTest.AddHook("custom-hook", expectedHook);
+
+        var serviceProvider = _services.BuildServiceProvider();
+
+        // Act
+        var actualHook = serviceProvider.GetKeyedService<Hook>("custom-hook");
+
+        // Assert
+        Assert.NotNull(actualHook);
+        Assert.Equal(expectedHook, actualHook);
+    }
+
     [Fact]
     public void AddHandler_AddsEventHandlerDelegateWrapperAsKeyedService()
     {