Add metadata model to Company (#3895)

* Add Metadata mixin to Company model

* Add migration file

* Lint

* Fixes due to style

* Syntax error

* Lint

* as this exposes a new endpoint to the API, increment the API version number with a brief description:

InvenTree/company/migrations/0049_company_metadata.py

@@ -0,0 +1,18 @@
+# Generated by Django 3.2.16 on 2022-11-02 17:53
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('company', '0048_auto_20220913_0312'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='company',
+            name='metadata',
+            field=models.JSONField(blank=True, help_text='JSON metadata field, for use by external plugins', null=True, verbose_name='Plugin Metadata'),
+        ),
+    ]