fix: use core.Uuid{} zero values consistently in policy.go

Replace uuid.UUID{} zero-value returns with core.Uuid{} in the Create
method error branches to maintain consistent UUID type references
throughout the transition to schemas core.Uuid.

Signed-off-by: Lee Calcote <lee.calcote@layer5.io>

Author: leecalcote

models/meshmodel/core/v1beta1/policy.go

@@ -49,12 +49,12 @@ func (p *PolicyDefinition) Create(db *database.Handler, hostID core.Uuid) (core.
 
 	mid, err := p.Model.Create(db, hostID)
 	if err != nil {
-		return uuid.UUID{}, err
+		return core.Uuid{}, err
 	}
 	p.ModelID = mid
 	err = db.Omit(clause.Associations).Create(&p).Error
 	if err != nil {
-		return uuid.UUID{}, err
+		return core.Uuid{}, err
 	}
 	return p.ID, nil
 }