Prompt for nickname on registration (#4)

Allow users to set a nickname while registering, controlled by settings. Also, add a setting to hide the username input entirely and randomly generate the username.

Co-authored-by: Sami Mazouz <sychocouldy@gmail.com>

extensions/nicknames/tests/phpunit.integration.xml

@@ -0,0 +1,24 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<phpunit
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/9.3/phpunit.xsd"
+    backupGlobals="false"
+    backupStaticAttributes="false"
+    colors="true"
+    convertErrorsToExceptions="true"
+    convertNoticesToExceptions="true"
+    convertWarningsToExceptions="true"
+    processIsolation="true"
+    stopOnFailure="false"
+>
+    <coverage processUncoveredFiles="true">
+        <include>
+            <directory suffix=".php">../src/</directory>
+        </include>
+    </coverage>
+    <testsuites>
+        <testsuite name="Flarum Integration Tests">
+            <directory suffix="Test.php">./integration</directory>
+        </testsuite>
+    </testsuites>
+</phpunit>