Added ApiUser and WhiteIp endpoints to REPP API

[maricavor]

Related to internetee/registrar_center2#93 Close internetee/registrar_center2#97

[viezly[bot]]

This pull request is split into 8 parts for easier review. 👀 Review pull request on Viezly

Changed files are located in these folders:

• app/controllers/repp/v1
• app/lib
• app/models
• config
• db
• lib/core_monkey_patches
• lib/gem_monkey_patches
• lib/serializers/repp
• test/fixtures
• test/integration
• test/models
• test/system/admin_area/registrars