fix(settings): Add Application Settings to Admin page

Allows the webmaster to set application settings

ref: #712 fixes #440

app/settings/admin.py

@@ -0,0 +1,51 @@
+from django.contrib import admin
+
+from settings.models.app_settings import AppSettings
+
+
+
+class AppSettingsAdmin(admin.ModelAdmin):
+
+    fieldsets = [
+        ( None,
+            {
+                "fields": [
+                    "owner_organization",
+                    'global_organization',
+                    'created',
+                    'modified',
+                ]
+            }
+        ),
+        ('Settings',
+            {
+                "fields": [
+                    "device_model_is_global",
+                    'device_type_is_global',
+                    "manufacturer_is_global",
+                    'software_is_global',
+                    'software_categories_is_global'
+                ]
+            }
+        ),
+    ]
+
+
+    def get_readonly_fields(self, request, obj=None):
+        if obj:
+            return ['owner_organization', 'created', 'modified' ]
+        else:
+            return []
+
+
+    def has_add_permission(self, request):    # Hide `Add` button when one item exists
+        if self.model.objects.count() >= 1:
+            return False
+        return super().has_add_permission(request)
+
+    def has_delete_permission(self, request, obj=None):    # Hide `Delete` Button
+        return False
+
+
+
+admin.site.register(AppSettings,AppSettingsAdmin)