[CT-2402] [Feature] Improve warnings/errors for constraints <> materialization types

[jtcohen6]

Views

If your model is materialized as a view and has constraints defined, those constraints are not supported & will be ignored, on ALL data platforms. We should raise a warning saying this, similar to the warn_unsupported functionality added in #7250.

Update: This might require calling a different macro within create_view_as, since all constraint parsing/rendering is currently happening within create_table_as → get_table_columns_and_constraints.

---

Ephemeral models

Parsing Error
  Constraint validation failed for: (models/sometable.sql)
  Only table, view, and incremental materializations are supported for constraints, but found 'ephemeral'

Let's just update the language here: "constraint validation" → "contract enforcement"

dbt-core/core/dbt/parser/schemas.py

Lines 969 to 988 in 87e25e8

	def validate_constraint_prerequisites(self, model_node: ModelNode):
	errors = []
	if not model_node.columns:
	errors.append(
	"Constraints must be defined in a `yml` schema configuration file like `schema.yml`."
	)
	if model_node.config.materialized not in ["table", "view", "incremental"]:
	errors.append(
	f"Only table, view, and incremental materializations are supported for constraints, but found '{model_node.config.materialized}'"
	)
	if str(model_node.language) != "sql":
	errors.append(f"Language Error: Expected 'sql' but found '{model_node.language}'")
	if errors:
	raise ParsingError(
	f"Constraint validation failed for: ({model_node.original_file_path})\n"
	+ "\n".join(errors)
	)

[emmyoop]

Doing this at parse time where we do model config/property validation makes more sense than creating a new macro that has to be implemented on all adapters.

[jtcohen6]

Let's review the validate_constraint_prerequisites method as well, see which validation we're actually still using/needing, and either remove or update the warnings accordingly