[Blazor] Support serialization extensibility for declarative persistent component state

[javiercn]

Currently we only serialize things as json. Ideally, we need an interface or something that you can implement (or pass as a parameter in the attribute) to provide a custom serialization mechanism.

The interface will be something like

public interface IPersistentComponentStateSerializer
{
    Task Persist(Type type, object instance, IBufferWriter buffer);
    void Restore(Type type, ReadOnlySequence<byte> data);
}

• Restore needs to be synchronous to avoid tearing on the UI.
• We don't want byte[] based APIs, as we want to minimize additional allocations if possible and we don't want to give the serializer the responsibility of allocating buffers.

Implementation Plan for Serialization Extensibility in Persistent Component State

Sample Registration

// Program.cs
var builder = WebApplication.CreateBuilder(args);

builder.Services.AddRazorPages();
builder.Services.AddServerSideBlazor();

// Register custom serializer as Singleton
builder.Services.AddSingleton<IPersistentComponentStateSerializer<User>, CustomUserSerializer>();

var app = builder.Build();

Task Checklist

1. Define the Serializer Interface

• Create IPersistentComponentStateSerializer interface
• Define PersistAsync(T value, IBufferWriter writer, CancellationToken cancellationToken) method
• Define Restore(ReadOnlySequence data) method (synchronous)
• Add appropriate XML documentation for the interface and methods

2. Update PooledArrayBufferWriter Integration

• Ensure PooledArrayBufferWriter from /src/Shared/PooledArrayBufferWriter.cs is accessible
• Verify compatibility with IBufferWriter interface for the Persist method
• Add any necessary using statements or references

3. Modify Persistent State Value Provider

• Update the persistent state value provider to attempt DI resolution of IPersistentComponentStateSerializer
• Implement fallback logic to use default JSON serialization when no custom serializer is found
• Handle type-specific serializer resolution
• Ensure proper error handling for serializer resolution failures

5. Maintain Backward Compatibility

• Ensure existing JSON serialization continues to work unchanged
• Verify no breaking changes to existing persistent component state APIs

6. Add Tests

• Unit tests for the new interface implementation