DecodeReferenceOrigins collects reference origins, using previously parsed AST (via [ParseStackConfiguration]), core schema of appropriate version (as obtained via [GetTerraformVersion]) and provider schemas ([PreloadEmbeddedSchema] or [ObtainSchema]).

DecodeReferenceTargets collects reference targets, using previously parsed AST (via [ParseStackConfiguration]), core schema of appropriate version (as obtained via [GetTerraformVersion]) and provider schemas ([PreloadEmbeddedSchema] or [ObtainSchema]).

LoadStackMetadata loads data about the stack in a version-independent way that enables us to decode the rest of the configuration, e.g.

LoadTerraformVersion loads the terraform version from the .terraform-version file in the stack directory.

ParseStackConfiguration parses the whole Stack configuration, i.e.

ReferenceValidation does validation based on (mis)matched reference origins and targets, to flag up "orphaned" references.