* MM-17549: use StatusNotFound when deleting plugin (#12983)
Trying to delete a plugin that does not exist should fail with a 404, not a 400.
Relates-to: https://mattermost.atlassian.net/browse/MM-17549
* MM-19630: marketplace: model ReleaseNotesURL (#13083)
Automatic Merge
* MM-20065: allow prepackaged plugin upgrade (#13076)
* MM-20065: allow prepackaged plugin upgrade
When locally installing prepackaged plugins, skip if a plugin exists with the same id and is the same or a newer version.
This is effectively a "poor man's" rework of prepackaged plugins to allow upgrade of prepackaged plugins via the marketplace. The larger plan to rework prepackaged plugins was deferred from v5.18.
Fixes: https://mattermost.atlassian.net/browse/MM-20065
* eliminate unnecessary installPlugin
* fix TestPluginSync defaults to match minio
* cleanExistingBundles
* close prepackaged filereader
* simplify