Label plugin refactor (#5251)

* Add skeleton for builtin label printing plugin

* Force selection of plugin when printing labels

* Enhance LabelPrintingMixin class

- Add render_to_pdf method
- Add render_to_html method

* Enhance plugin mixin

- Add class attribute to select blocking or non-blocking printing
- Add render_to_png method
- Add default method for printing multiple labels
- Add method for offloding print job

* Simplify print_label background function

- All arguments now handled by specific plugin

* Simplify label printing API

- Simply pass data to the particular plugin
- Check result type
- Return result

* Updated sample plugin

* Working on client side code

* Cleanup

* Update sample plugin

* Add new model type

- LabelOutput model
- Stores generated label file to the database
- Makes available for download

* Update label printing plugin mixin

* Add background task to remove any old label outputs

* Open file if response contains filename

* Remove "default printer" option which does not specify a plugin

* Delete old labels after 5 days

* Remove debug statements

* Update API version

* Changed default behaviour to background printing

* Update label plugin mixin docs

* Provide default printer if none provided (legacy)

* Update unit test

* unit test updates

* Further fixes for unit tests

* unit test updates

InvenTree/plugin/base/label/label.py

@@ -5,30 +5,26 @@ import logging
 from django.conf import settings
 from django.utils.translation import gettext_lazy as _
 
-import pdf2image
-
 import common.notifications
-from common.models import InvenTreeSetting
 from InvenTree.exceptions import log_error
 from plugin.registry import registry
 
 logger = logging.getLogger('inventree')
 
 
-def print_label(plugin_slug: str, pdf_data, filename=None, label_instance=None, user=None):
+def print_label(plugin_slug: str, **kwargs):
     """Print label with the provided plugin.
 
     This task is nominally handled by the background worker.
     If the printing fails (throws an exception) then the user is notified.
 
-    Args:
+    Arguments:
         plugin_slug (str): The unique slug (key) of the plugin.
-        pdf_data: Binary PDF data.
-        filename: The intended name of the printed label. Defaults to None.
-        label_instance (Union[LabelTemplate, None], optional): The template instance that should be printed. Defaults to None.
-        user (Union[User, None], optional): User that should be informed of errors. Defaults to None.
+
+    kwargs:
+        passed through to the plugin.print_label() method
     """
-    logger.info(f"Plugin '{plugin_slug}' is printing a label '{filename}'")
+    logger.info(f"Plugin '{plugin_slug}' is printing a label")
 
     plugin = registry.get_plugin(plugin_slug)
 
@@ -36,43 +32,30 @@ def print_label(plugin_slug: str, pdf_data, filename=None, label_instance=None,
         logger.error(f"Could not find matching plugin for '{plugin_slug}'")
         return
 
-    # In addition to providing a .pdf image, we'll also provide a .png file
-    dpi = InvenTreeSetting.get_setting('LABEL_DPI', 300)
-    png_file = pdf2image.convert_from_bytes(
-        pdf_data,
-        dpi=dpi,
-    )[0]
-
     try:
-        plugin.print_label(
-            pdf_data=pdf_data,
-            png_file=png_file,
-            filename=filename,
-            label_instance=label_instance,
-            width=label_instance.width,
-            height=label_instance.height,
-            user=user
-        )
+        plugin.print_label(**kwargs)
     except Exception as e:  # pragma: no cover
         # Plugin threw an error - notify the user who attempted to print
-
         ctx = {
             'name': _('Label printing failed'),
             'message': str(e),
         }
 
-        # Log an error message to the database
-        log_error('plugin.print_label')
-        logger.error(f"Label printing failed: Sending notification to user '{user}'")  # pragma: no cover
+        user = kwargs.get('user', None)
 
-        # Throw an error against the plugin instance
-        common.notifications.trigger_notification(
-            plugin.plugin_config(),
-            'label.printing_failed',
-            targets=[user],
-            context=ctx,
-            delivery_methods={common.notifications.UIMessageNotification, },
-        )
+        if user:
+            # Log an error message to the database
+            log_error('plugin.print_label')
+            logger.error(f"Label printing failed: Sending notification to user '{user}'")  # pragma: no cover
+
+            # Throw an error against the plugin instance
+            common.notifications.trigger_notification(
+                plugin.plugin_config(),
+                'label.printing_failed',
+                targets=[user],
+                context=ctx,
+                delivery_methods={common.notifications.UIMessageNotification, },
+            )
 
         if settings.TESTING:
             # If we are in testing mode, we want to know about this exception