Add priority for JavaScript plugins

[JammingBen]

Description

JavaScript plugins can now be registered with a specific priority. A higher priority means the plugin will be attached/detached before others.

I noticed this because core registers a plugin for OC.Share.ShareDialogView as well as the files_spaces app. These two conflict with each other because the core plugin needs to be registered first.

Related Issue

• Related to https://github.com/owncloud/files_spaces/issues/133

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Database schema changes (next release will require increase of minor version instead of patch)
• Breaking change (fix or feature that would cause existing functionality to change)
• Technical debt
• Tests only (no source changes)

Checklist:

• Code changes
• Unit tests added
• Acceptance tests added
• Documentation ticket raised: Priority parameter for JavaScript plugins docs#4149
• Changelog item, see TEMPLATE

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

64.3% Coverage
0.0% Duplication

[AlexAndBear]

Nice.
Another possible solution, would be that we enforce core plugins to get loaded first anyways,
I mean we may trap in a lot of problems if the core JS files are not loaded first properly.

What do you think @JammingBen?

[JammingBen]

I'd vote for keeping it configurable, just like we do it with storage wrappers. Maybe you want your app to be registered after core. Also I don't see nice a way to determine if a plugin comes from core or from an external app.

[mmattel]

Should'nt this also be added to the developer docs? @phil-davis fyi

[JammingBen]

@mmattel See docs issue: owncloud/docs#4149