Core: Move Checkstyle to the root pom.xml

[Net-burst]

🔧 Type of changes

• new bid adapter
• bid adapter update
• new feature
• new analytics adapter
• new module
• module update
• bugfix
• documentation
• configuration
• dependency update
• tech debt (test coverage, refactorings, etc.)

✨ What's the context?

Checkstyle enforcement does some basic code style checks and helps ensure that project code style remains coherent. The issue was that the Checkstyle was only applying to Prebid Server Core and not to modules.

🧠 Rationale behind the change

Code style enforcement should apply to the entire Prebid Server code base instead of only Prebid Server Core.

🔎 New Bid Adapter Checklist

• verify email contact works
• NO fully dynamic hostnames
• geographic host parameters are NOT required
• direct use of HTTP is prohibited - implement an existing Bidder interface that will do all the job
• if the ORTB is just forwarded to the endpoint, use the generic adapter - define the new adapter as the alias of the generic adapter
• cover an adapter configuration with an integration test

🧪 Test plan

How do you know the changes are safe to ship to production?

🏎 Quality check

• Are your changes following our code style guidelines?
• Are there any breaking changes in your code?
• Does your test coverage exceed 90%?
• Are there any erroneous console logs, debuggers or leftover code in your changes?

[Net-burst]

LGTM from my perspective. Thanks, @CTMBNara!

[osulzhenko]

LGTM