Queueing and mapping utilities for outbound data sync (#4881)

Add a registry for datasync providers and an associated sync queue, to be used by 
plugins that transfer data from pretix orders to external systems. 
Additionally, provide a generic data mapping interface to be used in settings pages 
of such plugins, to let users configure which information from pretix to fill into
which data fields of the external system.

---------

Co-authored-by: Raphael Michel <michel@rami.io>

src/pretix/control/logdisplay.py

@@ -43,9 +43,11 @@ from django.dispatch import receiver
 from django.urls import reverse
 from django.utils.formats import date_format
 from django.utils.html import escape, format_html
+from django.utils.safestring import mark_safe
 from django.utils.translation import gettext_lazy as _, pgettext_lazy
 from i18nfield.strings import LazyI18nString
 
+from pretix.base.datasync.datasync import datasync_providers
 from pretix.base.logentrytypes import (
     DiscountLogEntryType, EventLogEntryType, ItemCategoryLogEntryType,
     ItemLogEntryType, LogEntryType, OrderLogEntryType, QuestionLogEntryType,
@@ -421,6 +423,51 @@ class OrderPrintLogEntryType(OrderLogEntryType):
         )
 
 
+class OrderDataSyncLogEntryType(OrderLogEntryType):
+    def display(self, logentry, data):
+        try:
+            from pretix.base.datasync.datasync import datasync_providers
+            provider_class, meta = datasync_providers.get(identifier=data['provider'])
+            data['provider_display_name'] = provider_class.display_name
+        except (KeyError, AttributeError):
+            data['provider_display_name'] = data.get('provider')
+        return super().display(logentry, data)
+
+
+@log_entry_types.new_from_dict({
+    "pretix.event.order.data_sync.success": _("Data successfully transferred to {provider_display_name}."),
+})
+class OrderDataSyncSuccessLogEntryType(OrderDataSyncLogEntryType):
+    def display(self, logentry, data):
+        links = []
+        if data.get('provider') and data.get('objects'):
+            prov, meta = datasync_providers.get(identifier=data['provider'])
+            if prov:
+                for objs in data['objects'].values():
+                    links.append(", ".join(
+                        prov.get_external_link_html(logentry.event, obj['external_link_href'], obj['external_link_display_name'])
+                        for obj in objs
+                        if obj and 'external_link_href' in obj and 'external_link_display_name' in obj
+                    ))
+
+        return mark_safe(escape(super().display(logentry, data)) + "".join("<p>" + link + "</p>" for link in links))
+
+
+@log_entry_types.new_from_dict({
+    "pretix.event.order.data_sync.failed.config": _("Transferring data to {provider_display_name} failed due to invalid configuration:"),
+    "pretix.event.order.data_sync.failed.exceeded": _("Maximum number of retries exceeded while transferring data to {provider_display_name}:"),
+    "pretix.event.order.data_sync.failed.permanent": _("Error while transferring data to {provider_display_name}:"),
+    "pretix.event.order.data_sync.failed.internal": _("Internal error while transferring data to {provider_display_name}."),
+    "pretix.event.order.data_sync.failed.timeout": _("Internal error while transferring data to {provider_display_name}."),
+})
+class OrderDataSyncErrorLogEntryType(OrderDataSyncLogEntryType):
+    def display(self, logentry, data):
+        errmes = data["error"]
+        if not isinstance(errmes, list):
+            errmes = [errmes]
+        return mark_safe(escape(super().display(logentry, data)) + "".join("<p>" + escape(msg) + "</p>" for msg in errmes))
+
+
 @receiver(signal=logentry_display, dispatch_uid="pretixcontrol_logentry_display")
 def pretixcontrol_logentry_display(sender: Event, logentry: LogEntry, **kwargs):