Run migrations in a transaction (#60)

internal/db/migrations/postgres/02_oplog.up.sql

@@ -1,3 +1,5 @@
+begin;
+
 CREATE TABLE if not exists oplog_entry (
   id bigint generated always as identity primary key,
   create_time wt_timestamp,
@@ -37,3 +39,5 @@ values
   ('db_test_user', 1),
   ('db_test_car', 1),
   ('db_test_rental', 1);
+
+commit;

internal/db/migrations/postgres/03_db.down.sql

@@ -1,3 +1,7 @@
+begin;
+
 drop table if exists db_test_user;
 drop table if exists db_test_car;
-drop table if exists db_test_rental;
+drop table if exists db_test_rental;
+
+commit;

internal/db/migrations/postgres/03_db.up.sql

@@ -1,3 +1,5 @@
+begin;
+
 -- create test tables used in the unit tests for the internal/db package
 -- these tables (db_test_user, db_test_car, db_test_rental) are not part
 -- of the Watchtower domain model... they are simply used for testing the internal/db package
@@ -28,3 +30,5 @@ CREATE TABLE if not exists db_test_rental (
   user_id bigint not null REFERENCES db_test_user(id),
   car_id bigint not null REFERENCES db_test_car(id)
 );
+
+commit;