feat(host): add ILambdaOnInitContext for OnInit handlers

[j-d-ha]

Overview

Replace the existing OnInit delegate-based handlers with a custom ILambdaOnInitContext interface to provide a more extensible and centralized approach to handling initialization actions.

Current State

OnInit handlers currently use a delegate pattern which has limitations in terms of extensibility and discoverability.

Proposed Changes

1. Create ILambdaOnInitContext interface

   • Provides a structured context object for OnInit operations
   • Supports adding different kinds of information to the context
   • Enables more sophisticated initialization scenarios

2. Replace existing delegate pattern

   • Migrate from delegate-based handlers to context-based handlers
   • Provide a centralized location for building out OnInit handlers

3. Benefits

   • More discoverable and testable initialization handlers
   • Extensible context object that can grow with new requirements
   • Better separation of concerns for initialization logic
   • Type-safe access to initialization-specific information

Acceptance Criteria

• ILambdaOnInitContext interface is defined
• Existing OnInit delegate usage is replaced with context-based approach
• Handler registration supports the new context pattern
• Documentation updated to reflect new pattern
• Tests updated to cover new context-based handlers
• Migration path documented for existing users