Update Extensions Marketplace user preferences based on values from admin settings

MR:

• Use vscode_extension_marketplace settings in We... (!184067 - merged)
• Check marketplace_home_url with user opt in (!184569 - merged)

Description

Currently, there is a setting within user preferences that controls whether Extensions Marketplace is enabled in Web IDE and Workspaces. This references the Open VSX URL through this method.

We want to update this to reflect the Extension Marketplace configured through the admin settings. Additionally, we want to invalidate the user's opt in if the marketplace_home_url changes.

Acceptance Criteria

• Update the marketplace_home_url method to reference the URL of the Extensions Marketplace configured through the admin settings.
• Invalidate user's opt in when Extensions Marketplace URL changes. See "brainstorm" in implelmentation plan for proposed solution.

Questions:

• What's the timeframe of invalidation? If the URL's change, how do we want to affect open Web IDE / Workspaces? See below implementation plan for relevant brainstorm on how to address this.

Implementation Plan

brainstorm: Down the road we'll want to have a user opt-in to multiple extensions marketplace URL's at the same time (think .com, single user, bouncing across groups). To support this, we should start by adding a new db field in user_preferences for something like extensions_marketplace_opt_in_url and the opt_in is only valid if the current URL matches the one associated with the user.

note: Let's document the behavior of the Web IDE and Workspaces when the admin URL changes and user has opted in to the previous URL. We don't have to worry about this complexity right now.