chore: bootstrap module from working instance and add install guide

models/DonationProviderConfig.php

@@ -0,0 +1,44 @@
+<?php
+
+namespace humhub\modules\donations\models;
+
+use humhub\components\ActiveRecord;
+
+class DonationProviderConfig extends ActiveRecord
+{
+    public static function tableName()
+    {
+        return 'rescue_donation_provider_config';
+    }
+
+    public function rules()
+    {
+        return [
+            [['contentcontainer_id'], 'required'],
+            [['contentcontainer_id'], 'integer'],
+            [['paypal_enabled', 'paypal_recurring_enabled', 'stripe_enabled', 'stripe_recurring_enabled', 'sandbox_mode'], 'boolean'],
+            [['paypal_client_id', 'paypal_client_secret', 'paypal_webhook_id', 'stripe_publishable_key', 'stripe_secret_key', 'stripe_webhook_secret'], 'string', 'max' => 255],
+            [['default_currency'], 'string', 'max' => 8],
+            [['contentcontainer_id'], 'unique'],
+        ];
+    }
+
+    public function beforeSave($insert)
+    {
+        if (!parent::beforeSave($insert)) {
+            return false;
+        }
+
+        $now = date('Y-m-d H:i:s');
+        if ($insert && empty($this->created_at)) {
+            $this->created_at = $now;
+        }
+        $this->updated_at = $now;
+
+        if (empty($this->default_currency)) {
+            $this->default_currency = 'USD';
+        }
+
+        return true;
+    }
+}