feat(12.1-02): writable foreign keys, locked relation options, invisible columns

- FieldRelationContract.WritableForeignKey makes a belongsTo field over a
  protected foreign key writable; the protected key list is unchanged
- cabana.RelationLockProvider names related ids an administrator may not add
  or remove: options and labels carry locked, and a create or update that
  changes the locked subset is 403 before any row is written
- columns.yaml invisible keeps a column searchable and out of the rows
- a controller implementing pact.FilterOptions serves a scope filter's
  choices before the model
- SPA: locked chips and options in RelationField, DataTable skips invisible
  columns
- README, docs, OpenAPI document, TS types and dist updated

modules/pact/capabilities.go

@@ -583,8 +583,11 @@ type FilterScope interface {
 }
 
 // FilterOptions serves the choices of a model-backed config_filter scope
-// (D-27). It is implemented by the same model as FilterScope and receives the
-// filter's scope method name; labels may be phrase keys.
+// (D-27). It receives the filter's scope method name; labels may be phrase
+// keys. The admin controller may implement it and is asked first, so choices
+// that are read from the database can use the handle the controller holds;
+// otherwise the model that implements FilterScope is asked. The scope itself
+// is always the model's FilterScope.
 type FilterOptions interface {
 	FilterOptions(scope string) []Option
 }