[C#] Implement N+1 Query Solution with EF Core Include

[davideme]

Task

Implement the ?include= query parameter for eager loading in C#/Entity Framework Core.

Endpoints

• GET /buildings with ?include=rooms or ?include=rooms.lamps
• GET /buildings/{id} with ?include=rooms.lamps
• GET /buildings/{id}/rooms with ?include=lamps
• GET /rooms/{id} with ?include=lamps,building

Functional Requirement

Must minimize database queries regardless of the number of entities returned.

Implementation Hints

• Use EF Core's .Include() and .ThenInclude() methods
• Parse the include parameter and chain include calls dynamically
• Example: context.Buildings.Include(b => b.Rooms).ThenInclude(r => r.Lamps)

Acceptance Criteria

• ?include=rooms returns buildings with nested rooms
• ?include=rooms.lamps returns buildings with rooms and lamps
• Query count does not increase with number of buildings (verify with EF logging)

Parent Issue

Relates to #289