Handle functions with params in sort order.

Related to #1023

persistence/sql_base_repository_test.go

@@ -60,5 +60,15 @@ var _ = Describe("sqlRepository", func() {
 				Expect(sql).To(Equal("name asc, age desc, status desc"))
 			})
 		})
+		Context("function fields", func() {
+			It("handles functions with multiple params", func() {
+				sql := r.buildSortOrder("substr(id, 7)", "asc")
+				Expect(sql).To(Equal("substr(id, 7) asc"))
+			})
+			It("handles functions with multiple params mixed with multiple fields", func() {
+				sql := r.buildSortOrder("name desc, substr(id, 7), status asc", "desc")
+				Expect(sql).To(Equal("name asc, substr(id, 7) desc, status desc"))
+			})
+		})
 	})
 })