Support altering primary key columns

Closes #888

Author: kvch

pkg/migrations/op_common_test.go

@@ -30,6 +30,7 @@ type TestCase struct {
 	wantStartErr      error
 	wantRollbackErr   error
 	wantCompleteErr   error
+	beforeStart       func(t *testing.T, ctx context.Context, db *sql.DB, schema string)
 	afterStart        func(t *testing.T, db *sql.DB, schema string)
 	afterComplete     func(t *testing.T, db *sql.DB, schema string)
 	afterRollback     func(t *testing.T, db *sql.DB, schema string)
@@ -52,6 +53,10 @@ func ExecuteTests(t *testing.T, tests TestCases, opts ...roll.Option) {
 		t.Run(tt.name, func(t *testing.T) {
 			testutils.WithMigratorInSchemaAndConnectionToContainerWithOptions(t, testSchema, opts, func(mig *roll.Roll, db *sql.DB) {
 				ctx := context.Background()
+				if tt.beforeStart != nil {
+					tt.beforeStart(t, ctx, db, testSchema)
+				}
+
 				config := backfill.NewConfig()
 
 				// run all migrations except the last one