Comment 1 for bug 1468156

I believe the steps involved will be basically this (but maybe not in this order):

1. Move the files from htdocs/artefact/multirecipientnotification to htdocs/module/multirecipientnotification. Likewise relocate any theme and/or lang files.

2. Rename the PluginArtefactMultirecipientnotification class to PluginModuleMultirecipientnotification and make it extend PluginModule instead of PluginArtefact. Remove any unneeded PluginArtefact methods from the class.

3. Find all URLs and paths that reference artefact/multirecipientnotification, and rewrite them to refer to the new location module/multirecipientnotification

4. Force the new module plugin to be installed during system upgrade.

5. Copy the content from the old artefact's tables to the new module's tables. Or maybe just rename the tables? That would probably be faster. Although it would conflict with the tables auto-generated by the install.xml. Perhaps in the module's post_inst() method you could check for the artefact tables, and if they exist, drop the module tables and then rename the artefact tables to become the new module tables.

6. Drop the old artefact's triggers, and recreate them against the new module tables.

5. Delete any other lingering references to the plugin, from the database. It'll be in the "artefact_installed" table for instance.