Add loan history and add form to admin item detail view

Allows easier manipulation from

Drops the need of understanding what is an item and what is a loan : everything
can be done from item page.

Fix #189

hardware_provisioning/admin.py

@@ -56,6 +56,39 @@ class AvailabilityFilter(admin.SimpleListFilter):
             return queryset
 
 
+class LoanHistoryInline(admin.TabularInline):
+    model = Loan
+    extra = 0
+    readonly_fields = ('user', 'item', 'loan_date', 'loan_date_end', 'notes')
+    ordering = ['-loan_date_end']
+    verbose_name_plural = "Historique de prêt de cet objet"
+    show_change_link = True
+
+    def has_add_permission(self, request, obj=None):
+        return False
+
+    def has_delete_permission(self, request, obj=None):
+        return False
+
+
+class AddLoanInline(admin.StackedInline):
+    model = Loan
+    extra = 1
+    max_num = 1
+    fields = ('user', 'item', 'loan_date', 'notes')
+    verbose_name_plural = "Déclarer le prêt de cet objet"
+    classes = ['collapse']  # Django >= 1.10-ready
+
+    form = autocomplete_light.modelform_factory(Loan, fields='__all__')
+
+    def get_queryset(self, request):
+        qs = super(AddLoanInline, self).get_queryset(request)
+        return qs.none()
+
+    def has_delete_permission(self, request, obj=None):
+        return False
+
+
 @admin.register(Item)
 class ItemAdmin(admin.ModelAdmin):
     list_display = (
@@ -77,6 +110,8 @@ class ItemAdmin(admin.ModelAdmin):
 
     form = autocomplete_light.modelform_factory(Loan, fields='__all__')
 
+    inlines = [AddLoanInline, LoanHistoryInline]
+
     def give_back(self, request, queryset):
         for item in queryset.filter(loans__loan_date_end=None):
             item.give_back()