vague first draft of v3. TenantModelTest is passing

src/Database/Models/Concerns/CentralConnection.php

@@ -0,0 +1,11 @@
+<?php
+
+namespace Stancl\Tenancy\Database\Models\Concerns;
+
+trait CentralConnection
+{
+    public function getConnectionName()
+    {
+        return config('tenancy.central_connection');
+    }
+}

src/Database/Models/Concerns/GeneratesIds.php

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+<?php
+
+namespace Stancl\Tenancy\Database\Models\Concerns;
+
+trait GeneratesIds
+{
+    public static function bootGeneratesIds()
+    {
+        static::creating(function (self $model) {
+            if (! $model->id && config('tenancy.id_generator')) {
+                $model->id = app(config('tenancy.id_generator'))->generate($model);
+            }
+        });
+    }
+}

src/Database/Models/Concerns/HasADataColumn.php

@@ -0,0 +1,55 @@
+<?php
+
+namespace Stancl\Tenancy\Database\Models\Concerns;
+
+trait HasADataColumn
+{
+    public static function bootHasADataColumn()
+    {
+        $encode = function (self $model) {
+            foreach ($model->getAttributes() as $key => $value) {
+                if (! in_array($key, static::getCustomColums())) {
+                    $current = $model->getAttribute(static::getDataColumn()) ?? [];
+
+                    $model->setAttribute(static::getDataColumn(), array_merge($current, [
+                        $key => $value,
+                    ]));
+
+                    unset($model->attributes[$key]);
+                }
+            }
+        };
+
+        $decode = function (self $model) {
+            foreach ($model->getAttribute(static::getDataColumn()) ?? [] as $key => $value) {
+                $model->setAttribute($key, $value);
+            }
+
+            $model->setAttribute(static::getDataColumn(), null);
+        };
+
+        static::saving($encode);
+        static::saved($decode);
+        static::retrieved($decode);
+    }
+
+    public function getCasts()
+    {
+        return array_merge(parent::getCasts(), [
+            static::getDataColumn() => 'array',
+        ]);
+    }
+
+    /**
+     * Get the name of the column that stores additional data.
+     */
+    public static function getDataColumn(): string
+    {
+        return 'data';
+    }
+
+    public static function getCustomColums(): array
+    {
+        return array_merge(['id'], config('tenancy.custom_columns'));
+    }
+}