Add DATABASE_MAX_CONNS config setting

.env.template

@@ -20,6 +20,10 @@
 ## - https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNSTRING
 # DATABASE_URL=postgresql://user:password@host[:port]/database_name
 
+## Database max connections
+## Define the size of the connection pool used for connecting to the database.
+# DATABASE_MAX_CONNS=10
+
 ## Individual folders, these override %DATA_FOLDER%
 # RSA_KEY_FILENAME=data/rsa_key
 # ICON_CACHE_FOLDER=data/icon_cache