fix(setup): support mariadb in the installation wizard (#704)

Fixes InvoiceShelf/docker#79 — a fresh install using the shipped
docker-compose.mysql.yml cannot get past the database step, because that
compose file sets DB_CONNECTION=mariadb.

getDatabaseEnvironment() switched on sqlite, pgsql and mysql with no arm
for mariadb and no default, so it answered {"config":[]}. The wizard
chooses which form to render from database_connection in that response,
so step 4 rendered blank with no way forward — and nothing reached the
log, because the app never errored, it just replied with nothing.

Adds the mariadb arm, and a default so an unrecognised driver can never
again produce an unrenderable response: it is echoed back with the server
defaults, leaving the fields editable rather than the step empty.

MariaDB is now offered in the driver dropdown too. It was already a valid
DB_CONNECTION with its own connection in config/database.php, and the
form fields are identical to MySQL's.

Tested against the original code, where three of the new cases fail with
"Failed asserting that null is identical to 'mariadb'".

tests/Feature/Setup/DatabaseConfigurationTest.php

@@ -0,0 +1,58 @@
+<?php
+
+use function Pest\Laravel\getJson;
+
+/**
+ * The setup wizard picks which form to render from `database_connection` in this
+ * response. When the switch had no arm for the requested driver it returned an
+ * empty config, so step 4 rendered blank with no way to continue and nothing in
+ * the log — the app never errored, it just answered with nothing.
+ *
+ * That is what InvoiceShelf/docker#79 hit: the shipped docker-compose.mysql.yml
+ * sets DB_CONNECTION=mariadb, so a fresh install using the official compose file
+ * could not get past the database step.
+ */
+test('the database config endpoint answers with a usable config for every supported driver', function (string $connection) {
+    $response = getJson("/api/v1/installation/database/config?connection={$connection}");
+
+    $response->assertOk();
+
+    expect($response->json('config.database_connection'))->toBe($connection);
+})->with([
+    'mysql',
+    'mariadb',
+    'pgsql',
+    'sqlite',
+]);
+
+test('sqlite is told where its database file lives', function () {
+    $response = getJson('/api/v1/installation/database/config?connection=sqlite');
+
+    $response->assertOk();
+
+    expect($response->json('config.database_name'))->not->toBeEmpty();
+});
+
+test('server-based drivers are given a host and port to prefill', function (string $connection) {
+    $response = getJson("/api/v1/installation/database/config?connection={$connection}");
+
+    expect($response->json('config.database_host'))->not->toBeEmpty()
+        ->and($response->json('config.database_port'))->not->toBeEmpty();
+})->with([
+    'mysql',
+    'mariadb',
+    'pgsql',
+]);
+
+/**
+ * A driver we do not recognise must still produce something the wizard can
+ * render, rather than the empty config that caused #79.
+ */
+test('an unrecognised driver still returns a renderable config', function () {
+    $response = getJson('/api/v1/installation/database/config?connection=cockroach');
+
+    $response->assertOk();
+
+    expect($response->json('config.database_connection'))->toBe('cockroach')
+        ->and($response->json('config'))->not->toBeEmpty();
+});