Add history tracking functionality using django-pghistory; implement views, templates, and middleware for event serialization and context management

moderation/admin.py

@@ -2,6 +2,8 @@ from django.contrib import admin
 from django.contrib.admin import AdminSite
 from django.utils.html import format_html
 from django.urls import reverse
+from django.utils.safestring import mark_safe
+import pghistory
 from .models import EditSubmission, PhotoSubmission
 
 class ModerationAdminSite(AdminSite):
@@ -75,6 +77,33 @@ class PhotoSubmissionAdmin(admin.ModelAdmin):
                 obj.reject(request.user, obj.notes)
         super().save_model(request, obj, form, change)
 
+class HistoryAdmin(admin.ModelAdmin):
+    """Admin interface for viewing model history events"""
+    list_display = ['pgh_label', 'pgh_created_at', 'get_object_link', 'get_context']
+    list_filter = ['pgh_label', 'pgh_created_at']
+    readonly_fields = ['pgh_label', 'pgh_obj_id', 'pgh_data', 'pgh_context', 'pgh_created_at']
+    date_hierarchy = 'pgh_created_at'
+
+    def get_object_link(self, obj):
+        """Display a link to the related object if possible"""
+        if obj.pgh_obj and hasattr(obj.pgh_obj, 'get_absolute_url'):
+            url = obj.pgh_obj.get_absolute_url()
+            return format_html('<a href="{}">{}</a>', url, str(obj.pgh_obj))
+        return str(obj.pgh_obj or '')
+    get_object_link.short_description = 'Object'
+
+    def get_context(self, obj):
+        """Format the context data nicely"""
+        if not obj.pgh_context:
+            return '-'
+        html = ['<table>']
+        for key, value in obj.pgh_context.items():
+            html.append(f'<tr><th>{key}</th><td>{value}</td></tr>')
+        html.append('</table>')
+        return mark_safe(''.join(html))
+    get_context.short_description = 'Context'
+
 # Register with moderation site only
 moderation_site.register(EditSubmission, EditSubmissionAdmin)
 moderation_site.register(PhotoSubmission, PhotoSubmissionAdmin)
+moderation_site.register(pghistory.models.Event, HistoryAdmin)