add postgres and refactor code

model/position.go

@@ -9,3 +9,9 @@ type Position struct {
 	OrganizationID uint   `json:"organization_id" gorm:"index;not null"`
 	Users          []User `json:"users,omitempty"`
 }
+
+type PositionApi struct {
+	Name           string `json:"name" gorm:"unique;index"`
+	RightMask      int    `json:"right_mask"`
+	OrganizationID uint   `json:"organization_id" gorm:"index;not null"`
+}