.NET: Create end to end agent sample showing DI and Auth at all levels

[westey-m]

We need a sample that shows how to resolve all the different artifacts that attach to an agent from DI, including how to allow those to access resources that may require OBO tokens based on incoming requests.

The following artifacts should be featured:

1. Functions Tools
2. Custom ChatMessageStore
3. AI Context Providers
4. Middleware

For Function Tools it may also be useful to demonstrate how to modify the tool definition to expose a reduced signature with fewer parameters, and then how to inject values for the removed parameters at runtime.