Add models graph generation

Enjoy, fellow devs <3

README.md

@@ -186,6 +186,30 @@ Run:
     pytest
 
 
+Models graph
+------------
+
+You can build a huge PDF of the models used in coin with :
+
+    ./manage.py graph_models \
+      coin members offers billing resources reverse_dns configuration isp_database \
+      -o models.pdf \
+      --group-models
+
+You can tweak the app list to graph (eg: if you use [optional
+apps](#using-optional-apps)).
+
+For example, if you want to graph only the `hardware_provisioning` app, run :
+
+    ./manage.py graph_models \
+      hardware_provisioning
+      -o models.pdf \
+      --group-models
+
+And for more fine tunning of graph generation :
+
+    ./manage.py graph_models --help
+
 Available commands
 ==================
 

coin/settings_base.py

@@ -171,6 +171,7 @@ INSTALLED_APPS = (
     'activelink', #Detect if a link match actual page
     'compat',
     'hijack',
+    'django_extensions',
 
     'coin',
     'coin.members',

requirements.txt

@@ -2,6 +2,7 @@ Django>=1.8.17,<1.9
 psycopg2==2.5.4
 python-ldap==2.4.15
 wsgiref==0.1.2
+pydotplus==2.0.2
 python-dateutil==2.2
 django-autocomplete-light>=2.2.10,<2.3
 django-activelink==0.4
@@ -21,3 +22,5 @@ django-registration==2.2
 pytz>=2018.5
 unidecode>=1.0,<1.1
 django-debug-toolbar>=1.9.1,<1.10
+# Higher requires Django>=1.9
+django-extensions>=2.0,<2.1