Implement plugin settings in admin console

[mickmister]

The configuration for the plugin is currently handled directly in the server's config.json, which makes it difficult to manage since you can't use the MM UI to do so.

The task here is to declare these config settings in the plugin's plugin.json file, and implement any complex settings as a custom setting in the admin console.

[Kshitij-Katiyar]

@mickmister I have a clarification about this.
If this ticket is urgent just for the sake of this plugin working with the cloud servers. We can create a long text field, put that json into that field in the plugin configuration, and parse that from there. This would be a quick solution to make this work with cloud servers.
The second solution would be to create proper custom components in the web app to get all these settings from the plugin configurations. This would take longer as we are creating customs components and this would not work in mobile apps as well.

[mickmister]

@Kshitij-Katiyar This ticket is not urgent but is high impact, as mentioned here https://community.mattermost.com/core/pl/r385h5s83fbrjjk6yk3sc3aeqy

We can create a long text field, put that json into that field in the plugin configuration, and parse that from there. This would be a quick solution to make this work with cloud servers.

This has been a long time coming with this not being easy to configure. I would prefer if we use custom components instead, to make it easy to configure for on-prem admins as well.

This would take longer as we are creating customs components and this would not work in mobile apps as well.

This can't be configured on the mobile app today, and the goal of this ticket is not to support the mobile app. The settings are already living in the PluginSettings part of the server's config, so the admin console is the place to have this. This page is not accessible by the mobile, and that's fine for the purpose of this plugin/ticket.

[mickmister]

@Kshitij-Katiyar Note that there is progress on this, using the simpler approach you mentioned #92. However, I'm still thinking we should implement as custom components.

[Kshitij-Katiyar]

@mickmister I have made some components and also registered the same in the system console settings. Can you please take a look and give your suggestions for the same.

[mickmister]

@DHaussermann What are your thoughts on how this configuration UI looks?

[mickmister]

@Kshitij-Katiyar How does it look when writing the markdown message?

[mickmister]

@raghavaggarwal2308 Is this PR still being worked on? Brightscout#15

[mickmister]

Asking so we can determine whether to move forward with that PR or #92