update to refactored AshNeo4j

[matt-beanland]

Neo4j has been refactored for various reasons and while the dsl hasn't changed the refactor changes the persistence and supported types.

We need to explore a new type for characteristic value since term is not supported. It is possible it could be a tagged union of :struct, :integer, :float, :boolean, :string and arrays of same.

[matt-beanland]

Diffo.Provider.ProcessStatus is also a term. Again could be an Ash.Union of string and struct.

[matt-beanland]

Created a Diffo.Type.Value which is a :union type allowing :string, :boolean, :integer, :float, and struct
Compiles but many regression issues.
Specification calculations are the root of them.

[matt-beanland]

This was a major effort working with Claude for 3 days on both ash_neo4j and later diffo.

AshNeo4j

• Fixed PascalCase label derivation in persister — default labels now preserve CamelCase from module names (fixes delete guard failures)
• Added PascalCase verifier for all labels including domain labels
• Fixed can?/2 for expression calculations — returns false so Ash evaluates in memory
• Keyword field roundtrip support (previously merged PR)

Diffo

• Converted all expr/1 calculations to module-based calculations (SpecificationVersion, SpecificationHref, SpecificationInstanceType, InstanceHref) under Diffo.Provider.Calculations
• Updated Ash dependency
• Implemented Diffo.Type.Primitive — TypedStruct for TMF primitive values (string, integer, float, boolean, date, time, datetime, duration)
• Implemented Diffo.Type.Dynamic — self-describing typed value wrapper with cast_input, cast_stored, dump_to_native, apply_constraints
• Implemented Diffo.Type.Value — union of Primitive and Dynamic
• Implemented Diffo.Unwrap protocol with implementations for Value, Primitive, Dynamic, Ash.Union, Ash.CiString, Ash.NotLoaded
• Implemented Diffo.Unwrap.AshCustomExpression for use in Ash expressions
• Updated Diffo.Provider.Characteristic.value attribute to Diffo.Type.Value
• Updated all characteristic value inputs across provider, feature, relationship, instance test suites to use Value.primitive/2 and Value.dynamic/2
• Fixed ActionHelper / Instance.Characteristic / Instance.Feature to wrap DSL-declared characteristic values with Value.dynamic
• Fixed Assigner to unwrap/rewrap characteristic values correctly
• Renamed AssignableValue.type to assignable_type to avoid clash with Value union tag field
• Updated all test suites — provider, feature, relationship, instance, assigner all green
• Outstanding protocol implementations for Primitive and Dynamic via defoutstanding
• AshOutstanding.Union bug identified (type field overwrite) — issue raised
• TMF href format corrected (no name in path, standard /{type}/{id})

Known issues / follow-up

• Nil Value stored as %Ash.Union{type: :string, value: nil} instead of null — AshNeo4j nil suppression fix needed
• Primitive nil fields stored in Neo4j — AshNeo4j json_encode nil suppression needed
• Temporal types (date, time, datetime, duration) in Primitive not fully supported in nested JSON context — crowbar workaround via string for demo
• Value union tag field :type clashes with inner struct :type fields — needs rename to :kind or similar or just live with having to wrap with Value.dynamic wrapping. Primitive is OK as tag values have same meaning top and bottom.
• Ash.Type.Dynamic PR to upstream Ash — design proven, ready to propose