Make contractual schema items a Pydantic class/field value

[mferrera]

We are hardcoding contractual items in a place that is a bit difficult to discover. We can gain a lot of observability and more easily test that these items are not changed or removed by implementing something on the class level.

A simple implementation is just a contractual: bool = True on the class or field, but there might be some other way of accomplishing this that is more durable against changes, i.e., this variable doesn't add "real" protection against a committed change aside from the marking being there.

This also means we could populate the list of contractual items automatically rather than trying to remember to keep the list up-to-date.

fmu-dataio/src/fmu/dataio/_model/root.py

Lines 247 to 289 in c34f6dd

	schema = dict(
	ChainMap(
	{
	"$contractual": [
	"access",
	"class",
	"data.alias",
	"data.bbox",
	"data.content",
	"data.format",
	"data.grid_model",
	"data.is_observation",
	"data.is_prediction",
	"data.name",
	"data.offset",
	"data.seismic.attribute",
	"data.spec.columns",
	"data.stratigraphic",
	"data.stratigraphic_alias",
	"data.tagname",
	"data.time",
	"data.vertical_domain",
	"file.checksum_md5",
	"file.relative_path",
	"file.size_bytes",
	"fmu.aggregation.operation",
	"fmu.aggregation.realization_ids",
	"fmu.case",
	"fmu.context.stage",
	"fmu.iteration.name",
	"fmu.iteration.uuid",
	"fmu.model",
	"fmu.realization.id",
	"fmu.realization.name",
	"fmu.realization.uuid",
	"fmu.workflow",
	"masterdata",
	"source",
	"tracklog.datetime",
	"tracklog.event",
	"tracklog.user.id",
	"version",
	],

This requires a bit of research as to the best way to do it, since some classes represent a single field, or in same cases a single field within a class is contractual.

= Field(exclude=True) will keep it out of the schema.

[mferrera]

As a workaround for testing, can just pull the contractual list out so it can be accessed separately and added in as a constant list defined somewhere (i.e. definitions.py)