No such var: jdbc/with-transaction

Nobody has claimed this yet.

After following [this step](https://luminusweb.com/docs/guestbook#adding_some_tests) of the guestbook guide, I get the following when running `lein test`.

```
$ lein test
2020-07-14 20:42:51,454 [main] DEBUG org.jboss.logging - Logging Provider: org.jboss.logging.Slf4jLoggerProvider
Syntax error compiling at (guestbook/test/db/core.clj:20:3).
No such var: jdbc/with-transaction

Full report at:
/tmp/clojure-16884464781834444921.edn
Tests failed.
```

Sample code in the guide has the namespace set like so:

```
(ns guestbook.test.db.core
(:require
[guestbook.db.core :refer [*db*] :as db]
[luminus-migrations.core :as migrations]
[clojure.test :refer :all]
[clojure.java.jdbc :as jdbc]
[guestbook.config :refer [env]]
[mount.core :as mount]))
```

when initially after creating the project with `lein new luminus guestbook +h2 +immutant` it was originally:

```
(ns guestbook.test.db.core
(:require
[guestbook.db.core :refer [*db*] :as db]
[java-time.pre-java8]
[luminus-migrations.core :as migrations]
[clojure.test :refer :all]
[next.jdbc :as jdbc]
[guestbook.config :refer [env]]
[mount.core :as mount]))
```

Found that swapping out `[clojure.java.jdbc :as jdbc]` for `[next.jdbc :as jdbc]` and leaving out `[java-time.pre-java8]` seemed to work.

Only issue after that is `lein test` seems to use `guestbook_dev.db` instead of `guestbook_test.db`, where entries to the db during the test are persisted and can be seen afterwards on the webpage when doing a `lein run`.

Also curious why the db files are not included in the `.gitignore`.

generated using Luminus version "3.78"

Start with the generated guestbook/test/db/core.clj around line 20 and compare its namespace requires with the guide's example and the generated project. Run lein test and inspect whether it uses guestbook_dev.db or guestbook_test.db. Done means the guide and generated project agree, tests use the intended database, and the .gitignore question is resolved.

Written by the indexing model from the issue text.