Adds ENGINE to database config (#12458)

* adds ENGINE to database config #11791

* fixed lint issues

* updated doc

docs/configuration/required-parameters.md

@@ -33,11 +33,13 @@ NetBox requires access to a PostgreSQL 11 or later database service to store dat
 * `HOST` - Name or IP address of the database server (use `localhost` if running locally)
 * `PORT` - TCP port of the PostgreSQL service; leave blank for default port (TCP/5432)
 * `CONN_MAX_AGE` - Lifetime of a [persistent database connection](https://docs.djangoproject.com/en/stable/ref/databases/#persistent-connections), in seconds (300 is the default)
+* `ENGINE` - The database backend to use; must be a PostgreSQL-compatible backend (e.g. `django.db.backends.postgresql`)
 
 Example:
 
 ```python
 DATABASE = {
+    'ENGINE': 'django.db.backends.postgresql',
     'NAME': 'netbox',               # Database name
     'USER': 'netbox',               # PostgreSQL username
     'PASSWORD': 'J5brHrAXFLQSif0K', # PostgreSQL password
@@ -50,6 +52,9 @@ DATABASE = {
 !!! note
     NetBox supports all PostgreSQL database options supported by the underlying Django framework. For a complete list of available parameters, please see [the Django documentation](https://docs.djangoproject.com/en/stable/ref/settings/#databases).
 
+!!! warning
+    Make sure to use a PostgreSQL-compatible backend for the ENGINE setting. If you don't specify an ENGINE, the default will be django.db.backends.postgresql.
+
 ---
 
 ## REDIS

netbox/netbox/configuration_example.py

@@ -13,6 +13,7 @@ ALLOWED_HOSTS = []
 # PostgreSQL database configuration. See the Django documentation for a complete list of available parameters:
 #   https://docs.djangoproject.com/en/stable/ref/settings/#databases
 DATABASE = {
+    'ENGINE': 'django.db.backends.postgresql',  # Database engine
     'NAME': 'netbox',         # Database name
     'USER': '',               # PostgreSQL username
     'PASSWORD': '',           # PostgreSQL password

netbox/netbox/settings.py

@@ -182,15 +182,16 @@ if RELEASE_CHECK_URL:
 # Database
 #
 
-# Only PostgreSQL is supported
-if METRICS_ENABLED:
-    DATABASE.update({
-        'ENGINE': 'django_prometheus.db.backends.postgresql'
-    })
-else:
-    DATABASE.update({
-        'ENGINE': 'django.db.backends.postgresql'
-    })
+if 'ENGINE' not in DATABASE:
+    # Only PostgreSQL is supported
+    if METRICS_ENABLED:
+        DATABASE.update({
+            'ENGINE': 'django_prometheus.db.backends.postgresql'
+        })
+    else:
+        DATABASE.update({
+            'ENGINE': 'django.db.backends.postgresql'
+        })
 
 DATABASES = {
     'default': DATABASE,