Email history enhancement (#10114)

* add warning that the log is useless by default

* Add setting to enhance email log again

* add missing test for #10109

* add test for delete protections

* add error code

* Update email.md

* Update email.md

docs/docs/settings/email.md

@@ -38,4 +38,8 @@ Most popular providers are supported:
 
 Superusers can view the email log in the [Admin Center](./admin.md#admin-center). This is useful for debugging and tracking email delivery / receipt.
 
+!!! warning "Warning"
+    By default, email logs are cleaned after 30 days. This can be configured in the [InvenTree settings](../settings/global.md#server-settings).
+    If your organization is bound by business record retention laws or rules, you should ensure the retention of mail logs is set accordingly via a global override for the setting to ensure proper compliance. E.g. records in connection with commercial activity in the EU often have to be kept for over 5 years. Check requirements with proper sources for your region.
+
 {{ image("admin/email_settings.png", "Email Control Pane") }}

docs/docs/settings/error_codes.md

@@ -50,6 +50,12 @@ This might be caused by an addition or removal of models to the code base or cha
 The settings for SITE_URL and ALLOWED_HOSTS do not match the host used to access the server. This might lead to issues with CSRF protection, CORS and other security features.
 The settings must be adjusted.
 
+#### INVE-E8
+**Email log deletion is protected - Backend**
+
+The email log is protected from deletion by a setting. This was set by an administrator to prevent accidental deletion of emails.
+If you want to delete the email log, you need to get the [`INVENTREE_PROTECT_EMAIL_LOG`](../settings/global.md#server-settings) setting set to `False`.
+
 #### INVE-E9
 **Transition handler error - Backend**
 An error occurred while discovering or executing a transition handler. This likely indicates a faulty or incompatible plugin.

docs/docs/settings/global.md

@@ -41,6 +41,7 @@ Configuration of basic server settings:
 {{ globalsetting("INVENTREE_DELETE_ERRORS_DAYS") }}
 {{ globalsetting("INVENTREE_DELETE_NOTIFICATIONS_DAYS") }}
 {{ globalsetting("INVENTREE_DELETE_EMAIL_DAYS") }}
+{{ globalsetting("INVENTREE_PROTECT_EMAIL_LOG") }}
 
 
 ### Login Settings