Add CONN_MAX_AGE to documentation (#3642)

* Add CONN_MAX_AGE to sample configurations

* Correct alignment

* Restore ghost space

* Correct alignment.

* Use stable docs url

docs/configuration/required-settings.md

@@ -21,6 +21,7 @@ NetBox requires access to a PostgreSQL database service to store data. This serv
 * `PASSWORD` - PostgreSQL password
 * `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 (5432)
+* `CONN_MAX_AGE` - Number in seconds for Netbox to keep database connections open. 150-300 seconds is typically a good starting point ([more info](https://docs.djangoproject.com/en/stable/ref/databases/#persistent-connections)).
 
 Example:
 
@@ -31,6 +32,7 @@ DATABASE = {
     'PASSWORD': 'J5brHrAXFLQSif0K', # PostgreSQL password
     'HOST': 'localhost',            # Database server
     'PORT': '',                     # Database port (leave blank for default)
+    'CONN_MAX_AGE': 300,            # Max database connection age
 }
 ```
 

docs/installation/2-netbox.md

@@ -129,6 +129,7 @@ DATABASE = {
     'PASSWORD': 'J5brHrAXFLQSif0K', # PostgreSQL password
     'HOST': 'localhost',            # Database server
     'PORT': '',                     # Database port (leave blank for default)
+    'CONN_MAX_AGE': 300,            # Max database connection age
 }
 ```
 

netbox/netbox/configuration.example.py

@@ -17,6 +17,7 @@ DATABASE = {
     'PASSWORD': '',           # PostgreSQL password
     'HOST': 'localhost',      # Database server
     'PORT': '',               # Database port (leave blank for default)
+    'CONN_MAX_AGE': 300,      # Max database connection age
 }
 
 # This key is used for secure generation of random numbers and strings. It must never be exposed outside of this file.