Support trimmed/AOT applications by removing implicit dependency on reflection-based System.Text.Json serialization

[davidatwhiletrue]

Summary

When consuming Casper.Network.SDK from a .NET file-based application, JSON serialization fails with:

Reflection-based serialization has been disabled for this application.
Either use the source generator APIs or explicitly configure the
'JsonSerializerOptions.TypeInfoResolver' property.

The failure originates from RpcMethod.Serialize(), which assumes reflection-based System.Text.Json serialization is available.

Why this matters

Modern .NET applications (including trimmed, Native AOT, and some file-based app scenarios) may disable reflection-based JSON serialization by default. As a result, the SDK cannot be used without consumers explicitly changing their application configuration.

A reusable SDK should ideally not depend on this application-level setting.

Proposed solution

Preferred (long-term)

Adopt System.Text.Json source generation (JsonSerializerContext) for all request and response types used by the SDK.

Benefits:

• Supports trimmed applications.
• Supports Native AOT.
• Removes the SDK's dependency on reflection-based serialization.
• Improves startup performance.
• Follows Microsoft's recommended approach for modern .NET libraries.

Possible short-term workaround

Where JsonSerializerOptions are created, configure a DefaultJsonTypeInfoResolver when no resolver has been supplied by the application.

Reproduction

1. Create a .NET file-based application.
2. Reference the SDK using #:project.
3. Invoke an RPC method such as GetAccountInfo().
4. Observe the exception during request serialization:

Reflection-based serialization has been disabled for this application.
Either use the source generator APIs or explicitly configure the
'JsonSerializerOptions.TypeInfoResolver' property.

Additional notes

Although this was first encountered from a .NET file-based app, the underlying issue is not specific to file-based apps. It can affect any application that disables reflection-based System.Text.Json serialization (for example, trimmed or Native AOT applications).