Add Eslint rules to throw error when importing other modules from within modules directory.

[Fawke]

Type of change

• Feature

Description of change

Related to #3964.

[jsnellbaker]

@Fawke

This does look good overall, though I'm not sure about the exceptions made for the prebidServer and userId sub-folders. Can we restructure the logic to still allow the rules there? I get it was done to allow the config file to be imported, but I'm curious if there's another way to go about this.

[snapwich]

Just noticed this pull-request. I made a similar stab at it in #3976

If we can get public eslint plugins to work through configuration I think that's preferable; not sure if it's possible though so I ended up making a custom plugin. Some of things I wanted were:

• a whitelist of modules allowed per directory paths (as opposed to a blacklist, or restrictions as you have here)), it might be possible with eslint-plugin-import but I couldn't get it working quite right.
• validate that modules can be resolved and are not module entry points. The first part can be handled with eslint-plugin-import but I'm not sure about the later part.

If you can get those constraints working with this pull-request then I'm all for it, I'm not sure no-restricted-imports and no-restricted-modules are the rules we want though.

[jaiminpanchal27]

Closing this PR in favour of #3976