Add cpmDistribution function for Google Analytics adapter

[muuki88]

Type of change

• Bugfix
• Feature
• New 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

Add an additional option cpmDistribution to the google analytics adapter to allow customization of the cpm buckets.

[msm0504]

Are there unit tests to go with these changes? Looks like few tests have been written for the googleAnalyticsAdapter as a whole

[muuki88]

The test coverage of the analytics adapter is rather poor. I can try to add more if you think this makes sense, but I would appreciate some hints as I'm not sure how to mock things to verify the proper methods are being called.

Also the implementation with a separate queue is a bit strange as GA already provides an API for that, which may make tests even trickier.

[muuki88]

I added a test without the mocking stuff. I'm puzzled that I can't call enableAnalytics twice, which makes it impossible to write isolated test cases. The AdapterManager doesn't seem to override this method, but it hell looks like it 😄

[msm0504]

The code change to the adapter seems fine to me, so I'll approve this.

I'll ask in the prebid-js slack about writing the tests, since those should be added for the adapter as a whole.