Introduced `EnvelopeGeneratorOptions` and `SqlCacheOptions` to enable fine-grained control over optional service registrations in `AddEnvelopeGenerator`. Updated `AddEnvelopeGenerator` to conditionally register services like `HttpContextAccessor`, `DistributedSqlServerCache`, `Dispatcher`, `MemoryCache`, and `UserManager` based on these options.
Updated `DependencyInjection.csproj` to include necessary framework references and package dependencies. Simplified `Program.cs` by consolidating service registrations into `AddEnvelopeGenerator`, reducing boilerplate and improving maintainability.
Improved extensibility by centralizing service registration logic, allowing consuming projects to customize configurations without modifying the core library. Updated documentation and removed unused directives.
