Permutive Identity Manager: initial implementation

[talbotja]

Type of change

• Bugfix

• Feature (new userId submodule)

• New bidder adapter

• Updated bidder adapter

• Code style update (formatting, local variables)

• Refactoring (no functional changes, no api changes)

• Build related changes

• CI related changes

• Does this change affect user-facing APIs or examples documented on http://prebid.org?

• Other

Description of change

This PR adds a new userId submodule, permutiveIdSystem, which will support Permutive customers in using Permutive's Identity Manager product.

The basic idea is that Permutive's customer can configure which identity providers they want to work with via Permutive's dashboard, and Permutive's SDK, running on the customer's site, will take care of retrieving the relevant IDs and storing them in localStorage. The job of this module is to take those IDs from localStorage and make them available to prebid bidders.

[AntonioGargaro]

Question to prebid maintainers, if we were to make this a getter property such that we could read the eids config directly from our SDK and use what we have defined here as a fallback, would this propagate to other parts of the identity system as it would be called frequently? Or is the initial object returned stored by reference somewhere?

i.e.

get eids() {
  const data = read.from.permutive.sdk
  if (data) {
    return data
  }

  return { id5id: ... }
}

[JulieLorin]

LGTM