Fixed #6725 - revert auro_increment_prefix to string

This was mis-migrated as boolean.

It’s essentially a duplicate migration, as it is fixed in-place on the existing migration, and then a new migratio was created to handle anyone who already upgraded.

database/migrations/2019_02_14_154310_change_auto_increment_prefix_to_nullable.php

@@ -14,7 +14,7 @@ class ChangeAutoIncrementPrefixToNullable extends Migration
     public function up()
     {
         Schema::table('settings', function (Blueprint $table) {
-            $table->boolean('auto_increment_prefix')->nullable()->default(null)->change();
+            $table->string('auto_increment_prefix')->nullable()->default(null)->change();
         });
     }
 

database/migrations/2019_02_16_143518_auto_increment_back_to_string.php

@@ -0,0 +1,30 @@
+<?php
+
+use Illuminate\Support\Facades\Schema;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Database\Migrations\Migration;
+
+class AutoIncrementBackToString extends Migration
+{
+    /**
+     * Run the migrations.
+     *
+     * @return void
+     */
+    public function up()
+    {
+        Schema::table('settings', function (Blueprint $table) {
+            $table->string('auto_increment_prefix')->nullable()->default(null)->change();
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     *
+     * @return void
+     */
+    public function down()
+    {
+        //
+    }
+}