Add 'CableTypes' (#406)

* Move relevant fields and create migration to autogen cable types

* CRUD and ordering

* FIX: Prevent creating duplicate cable types

* FIX: pep8/remove debug print

* FIX: Meta migrations... :>

* FIX: Update tests to match new UX

* Move cabletype menu links into 'Assets' dropdown

* Fix migration

* Specify version of reportlab

Should fix CI - looks like I went a bit too ham-handed in my requirements.txt purge last time...

assets/forms.py

@@ -1,6 +1,7 @@
 from django import forms
 
 from assets import models
+from django.db.models import Q
 
 
 class AssetForm(forms.ModelForm):
@@ -34,3 +35,17 @@ class SupplierForm(forms.ModelForm):
 
 class SupplierSearchForm(forms.Form):
     query = forms.CharField(required=False)
+
+
+class CableTypeForm(forms.ModelForm):
+    class Meta:
+        model = models.CableType
+        fields = '__all__'
+
+    def clean(self):
+        form_data = self.cleaned_data
+        queryset = models.CableType.objects.filter(Q(plug=form_data['plug']) & Q(socket=form_data['socket']) & Q(circuits=form_data['circuits']) & Q(cores=form_data['cores']))
+        # Being identical to itself shouldn't count...
+        if queryset.exists() and self.instance.pk != queryset[0].pk:
+            raise forms.ValidationError("A cable type that exactly matches this one already exists, please use that instead.", code="notunique")
+        return form_data