Fix user search field in OAuthCredentials admin

arkindex/users/admin.py

@@ -127,7 +127,16 @@ class OAuthCredentialAdmin(admin.ModelAdmin):
     list_filter = [('status', EnumFieldListFilter), ]
     fields = ('id', 'user', 'token', 'refresh_token', 'expiry', 'status')
     readonly_fields = ('id', )
-    search_fields = ('user', )
+    search_fields = ('searchable_email', )
+
+    def get_queryset(self, request):
+        qs = super().get_queryset(request)
+        qs = qs.select_related('user')
+        # Django's search uses ILIKE, but LIKE is not supported in PostgreSQL with nondeterministic collations.
+        # We are using a case-insensitive collation to get unique case-insensitive emails, so to search properly,
+        # we first have to set the collation back to its default value, making it case-sensitive again;
+        # since Django uses ILIKE, it will be case-insensitive anyway.
+        return qs.annotate(searchable_email=Collate('user__email', 'default'))
 
 
 admin.site.register(User, UserAdmin)