Implement BusinessDocumentBase combining BusinessBase and BusinessListBase

[rockfordlhotka]

Summary

• Implements BusinessDocumentBase<T,C>, a new base class that inherits from BusinessBase<T> and adds full BusinessListBase<T,C> collection capabilities
• Enables the "document pattern" where a single business object has its own managed properties, validation rules, and authorization AND contains a collection of child items
• Adds IBusinessDocumentBase<C> consolidated interface

Key Features

• Full IList<C> collection support via composition (MobileList<C>)
• Deleted child tracking (IContainsDeletedList)
• N-level undo cascading to collection children
• IsDirty/IsValid/IsBusy aggregation across properties and children
• MobileFormatter serialization of collection items
• CollectionChanged/PropertyChanged events
• LoadListMode for bulk loading without events
• Child data access (Child_Update/Child_UpdateAsync)
• RegisterProperty / RegisterMethod with correct type resolution

Test plan

• 29 unit tests covering:
  • Create and fetch operations
  • Collection operations (Add, Insert, Remove, RemoveAt, Clear, Contains, IndexOf, Enumerator, Indexer)
  • Status aggregation (IsDirty, IsValid, IsNew across properties and children)
  • CollectionChanged events
  • Clone / serialization preservation
  • N-level undo (BeginEdit/CancelEdit/ApplyEdit for properties and children)

Closes #1830

🤖 Generated with Claude Code

[hurcane]

I looked for a related discussion or issue for this PR, but didn't find one. What is the intended utility for this kind of class?

Looking at this initial plan, I wonder how more complex documents would be handled. By more complex, I mean having multiple child lists. In the invoice example, the editable Invoice class in my project would also have a comments collection, a contacts collection. Thinking across the full project, I don't have any documents with only a single collection.

[StefanOssendorf]

You are describing a business (base) object. I think the purpose of this PR is to get the whole rules stuff etc. into a business list class.
For example you have a PositionList which has rules to enforce (e.g. only one item with Type X is allowed) and so on. This kind of rule is currently not possible because the list itself can't define rules.

[hurcane]

I get that use case. Those business rules currently have to be handled in the parent class. We typically use properties on the child classes to indicate their error state. For example, the child will have an IsDuplicate property with a rule that ensures the property is false.

I'm all for simplifying this scenario, but it wasn't clear in the description and the generated plan. Sorry for butting in without understanding the full context.

[rockfordlhotka]

I get that use case. Those business rules currently have to be handled in the parent class. We typically use properties on the child classes to indicate their error state. For example, the child will have an IsDuplicate property with a rule that ensures the property is false.

I'm all for simplifying this scenario, but it wasn't clear in the description and the generated plan. Sorry for butting in without understanding the full context.

#1830