* feat: yarn 2

* Apply suggestions from code review

Co-Authored-By: Michael Kriese <michael.kriese@visualon.de>

* refactor: move yarnMajorVersion test

* test: apply patch from @JamieMagee

see https://github.com/renovatebot/renovate/pull/5657#issuecomment-611205192



* test: update snapshots

* prettier-fix

Co-authored-by: Michael Kriese <michael.kriese@visualon.de>
Co-authored-by: Jamie Magee <jamie.magee@gmail.com>

Co-authored-by: Renovate Bot <bot@renovateapp.com>

validator was removed in 707d35db

Co-authored-by: Michael Kriese <michael.kriese@visualon.de>

* chore(deps): update dependency prettier to v2

* Run prettier-fix

Co-authored-by: Renovate Bot <bot@renovateapp.com>
Co-authored-by: Jamie Magee <jamie.magee@gmail.com>

Co-authored-by: Renovate Bot <bot@renovateapp.com>

* build(deps): update dependency azure-devops-node-api to v10

* chore: update jest snapshots

Co-authored-by: Renovate Bot <bot@renovateapp.com>
Co-authored-by: Jamie Magee <jamie.magee@gmail.com>

Adds an optional new object `defaultConfig` to datasources. This object will be merged into config during the update flattening process, and before the last applyPackageRules. i.e. it can still be overridden by packageRules.

Co-authored-by: Jamie Magee <JamieMagee@users.noreply.github.com>

Co-authored-by: Michael Kriese <michael.kriese@visualon.de>